A/N: So this is probably set sometime early season 4? Or, if you want to ignore the fact that Lancelot and Elyan are still alive, then sometime towards the end of Season 5 but before the finale :)
1) Merlin had quite the head for figures and budgets
It seemed to come as much of a surprise to Merlin himself as it did to Arthur when they'd discovered fairly early on in Merlin's service to him that Merlin was quite good with numbers.
Growing up a peasant in Ealdor, Merlin's mother may have taught him very rudimentary reading and writing skills, and he had learned basic counting out of the necessity of life, but Merlin had never had much of a chance to use reading and writing until he'd come to Camelot, and certainly never a chance to learn his formal numbers, or to do anything more complicated with them than making sure he and his mother had enough food stored to get through the winter.
In fact, Merlin had never seen numbers written down until he'd come to Camelot, and he hadn't really even gotten comfortable and good with reading and writing until he'd gotten to Camelot and got to practice more with some of Gaius' books.
But despite what Arthur often teased, Merlin was quite intelligent; intelligent enough that he had finished teaching himself how to read and write by practicing with the books he now had access to in Camelot.
The real break-through moment, however, was perhaps a month or two into his service to Arthur. Merlin had as usual been serving him when he'd had lunch with his father.
During that particular lunch, Uther had wanted to discuss a village that had had a wildfire burn through most of it's crops, and where they were going to get the money to supply the village not only with supplies not to starve the following year, but also to replant next year.
The village had a bridge over a particularly hard-to-cross river as well that was very well-traveled, and they would need the money to upkeep the bridge if they were not going to gain a profit from the harvest this fall.
Uther had put Arthur in charge of figuring out a plan for the village, so after lunch Arthur had retired to his desk in his chambers to work the numbers.
The most obvious way to get the village some money was to put a toll on the bridge, which could go towards the upkeep of the bridge and possibly a bit towards supplies for the coming year.
But there was no way it was going to pay for everything needed unless the toll was much higher than what most people would be willing or able to pay to cross the bridge.
Arthur had been beginning to get frustrated, because he knew his father wanted a solution that didn't involve paying directly from the royal treasury if all possible, when Merlin spoke up from where he'd been making Arthur's bed and putting away his clothes.
"Arthur? Can I make a suggestion?"
Arthur had sighed. "Merlin, this is a rather complicated matter of state that I wouldn't expect you to understand."
"But I think I may have an idea of where you could get the money."
Arthur blinked, surprised. "Well, alright then. What is it?"
Merlin then began to lay out his rather impressive idea of getting a little money here and there from several different areas in the budget, and moving a bit of money around, until it added up to enough to take care of the village, but not enough from any one area of the budget to be missed after a bit of shuffling of resources.
Merlin didn't have specifics when he started explaining - he didn't know the exact numbers of what things cost, or exactly how much was in each area of the budget - but the general idea was sound, and he'd proven that he'd been paying more attention that Arthur had given him credit for in meetings and discussions as he had a rough idea of what could be trimmed off different areas to have a little extra to throw towards the village.
When Arthur had invited him over to the table to look at the actual numbers, that's when Merlin had to (somewhat sheepishly) admit that he hadn't actually seen written numbers before, so didn't know the symbols that Arthur had on his paper to represent them.
So, after Arthur had finished figuring out the village issue for his father, he and Merlin sat down and he taught Merlin his numbers. Once Merlin had them down, it didn't take much for him to be able to do more, rather advanced figures. And what was more, Merlin enjoyed doing them. Which was convenient, since Arthur did NOT.
And Arthur would never admit it, but Merlin was actually a bit better than him at it anyway, so at times he would consult Merlin in similar situations to the village, or when he needed to add up and give his father the yearly report on how much it cost to pay, equip, and train his knights.
Over the months and years it became second nature to have Merlin go over the numbers with him. By an unspoken agreement, neither Merlin nor Arthur mentioned it in public, because Uther would not only disapprove of Arthur deferring to a servant, but he certainly disapprove of giving said servant potentially confidential state information.
When Arthur became king, he gave Merlin even more leeway over the books, at times allowing him to write up the budgets much like he did Arthur's speeches. It was much more open, but by then it was a habit not to advertise it, even if it was something they didn't think about anymore.
Nevertheless, they hadn't even quite consciously realized they were still keeping it only between then until after Arthur had married Guinevere, and one day not too long after, when they were still rebuilding from the damage from the battle to take Camelot back from Morgana, Arthur had come into his chambers after a meeting with some council members about the repairs and the labour and the cost of them.
Arthur had permitted Merlin to come up with a budget to fit in the wedding and repairs, as he'd been concentrated on all the politics and restructuring and, well, everything a King needs to do after taking back his kingdom when it had been forcibly taken from him. Not to mention the whole getting married thing.
So he knew the whole gloomy financial prospect the council was thinking they were in was not exactly true, but he couldn't recall everything Merlin had juggled around with the budget to make it so.
When he arrived in his chambers, Merlin putting away some recently cleaned clothes and Gwen was sitting in a chair by the window, taking in the sunlight as she did some embroidery.
Arthur gave a smile and quick kiss to the hair in greeting to his wife, then he strode to his desk.
"Merlin, some of the council seem to be under the impression that we spent much more on the wedding than we actually did, and that when combined with the repair work for the castle and such, that Camelot is in dire financial straights. I know you had this all worked out somehow before the wedding, that it may be tight but we aren't that bad off...can we go over it so can I explain it to the council tomorrow?"
Merlin joined him at the desk, both of them looking down at the parchment Arthur was spreading out.
Gwen's surprised voice stopped them as she blurted, "Merlin had it all figured out?"
Arthur and Merlin both looked up at her and blinked. "Umm...yes?" Merlin said hesitantly.
Arthur chuckled. "Turns out Merlin is quite good with numbers, as shocking as it may be to hear he has an actual useful skill."
Merlin scowled. "Shall I leave you to figure it out and explain it to your council tomorrow on your own, my lord?"
Arthur promptly looked rather horrified as he glanced from Merlin to the paper, obviously thinking of the headache of doing the math on his own, which he knew Merlin just might make him do. He hated the boredom of figuring on his own, and he knew that Merlin knew this quite well.
At least when Merlin was at the desk as well, helping him, it was bearable.
Merlin rolled his eyes at Arthur's expression and sighed as he turned back to the table. "Come on, prat, we better get this figured out before the council panics."
Arthur gratefully pulled the parchment over towards them so they could get to work.
2) Merlin actually takes pride in his work when it matters (or at least in his King)
For all of the hard time Arthur gives him, Merlin is actually competent at his job when he's not disappearing for no apparent reason letting Arthur think he's been in the tavern (for more on that, see numbers 4 and 5 of things Arthur knows about Merlin).
As with the numbers, Merlin is a fast learner, and for one who grew up no where near a court or nobles, it doesn't take long at all before (at least in public, official settings, or in front of visiting nobles) Merlin is expertly acting the part of the manservant to the royal family.
The fact that half the time he doesn't act like he should towards Arthur or others in the inner circle of the court (such as the knights and Gwen) in private isn't because Merlin doesn't know how he's SUPPOSED to act, Arthur knows, but more because Merlin is just that stubborn and pig-headed. Also because Arthur likes the fact that he's not a bootlicker.
The point of all this was that Merlin could be a great manservant when he put his mind to it. And especially since Arthur had become king, Merlin put his mind to it whenever there were visiting nobles.
In those situations, Merlin always made sure his clothes were always freshly washed and ironed, his crown and boots polished to perfection, his armor gleaming ready for the tournaments that were often held in the noble's honor, and picked out his clothes with great care.
It was another one of those things that Arthur and Merlin didn't really talk about until pushed to talk about by someone else. That someone else, as was becoming a habit since their marriage, was Guinevere.
The first time they had nobles worth impressing visit since their wedding (so the first time since Gwen was Queen), Gwen had been rather surprised when, the day before they arrived, after Merlin woke them with breakfast and they were eating at the table, Arthur said to Merlin, "Now, Merlin, don't forget, with Sir Ector and his company coming tomorrow I'm going to get in training all day today with the knights as I won't be able to as much as normal for most of the week they are here. We'll need lunch, so have the kitchens prepare something that can be eaten outside, and quite a lot of it as I will have many knights training. I know you'll likely be very busy today, but don't forget."
Merlin rolled his eyes and grumbled a bit as he refilled their cups with drink. "You know I'll be busy, yet you add to that anyway."
"Why will you be so busy today, Merlin?" Gwen asked curiously.
"Getting ready for tomorrow." Merlin answered. "Which reminds me, Gwen, if you have time after breakfast I need you to help pick out the jewels you want to wear tomorrow. I'll need to polish them."
Arthur didn't know whether to be amused, touched, or concerned that Merlin had now apparently included Gwen in his attempt at perfection.
Gwen just stared at Merlin in surprise. Arthur couldn't blame her..normally, with the exception of Arthur's armor, Merlin didn't polish without being asked or unless something rather badly needed it.
The rest of the day, Merlin was indeed very busy. Gwen reported, when she stopped by and spoke to Arthur during a water break during his training, that Merlin had been going full-stop all day, hauling water to wash clothes and bedding, sweeping and scrubbing the floors.
"And now you he's going to have to bring down lunch for you and the knights. Surely we can have another servant do it."
"Guinevere, when he brings the lunch down, we can bully him into sitting and eating with us. And that will be the only break he will take all day."
Gwen's face softened. "You asked him to bring the lunch so you could force him to take a break from working."
Arthur huffed. "Don't tell him, whatever you do. But yes, that's the general idea. He always goes a bit overboard when we have visitors we need to impress."
Gwen took his hand. "That explains why you always look so very much like the great king you are when you greet them; because Merlin makes certain of it."
Arthur rolls his eyes to try and hid his affection for his servant and the warmth her praise brought him. "He's my manservant, Guinevere, he is supposed to make certain I look presentable. The fact that you're commending him for actually doing his job just shows how much he normally doesn't."
Gwen chuckled. "Perhaps, but did you not just say yourself he goes overboard? And do you forget that I was a servant myself? I know he is not required to wash our clothes we are going to wear tomorrow just to freshen them up if they are already clean."
Arthur's eyebrows rose. "Our clothes?"
Gwen nodded. "Yes, he had me pick out the dress I wanted for tomorrow along with the jewelry I wanted to wear with it, and laid them out next to your clothes and crown to wash and polish." Her smile turned teasing. "It appears making me look just as good is now part of making certain you and your kingdom are represented properly, my lord."
Arthur sighed. "I have told him before that he didn't have to go quite so enthusiastic with the clothes and cleaning, as long as my good clothes were clean and crown polished appropriately. He told me that I tell him he's the worst manservant in all of Albion quite enough, he didn't need other nobles sharing the opinion."
Gwen squeezed his hand and with a gentle smile said softly, "Merlin takes pride in his king, and wants others to see what we do in you."
Arthur had to swallow around a lump in his throat. With anyone else, Arthur may not have let on about how touched he felt by Merlin's unfailing loyalty and pride in him, but this was Gwen, his wife and love.
"Yes, I suppose he does."
3) Most of the round-table knights would be more loyal to Merlin than to Arthur if push came to shove
Yes, Arthur was aware that most of his closest knights had been friends with or been helped by Merlin before they became his knights. So yes, he was aware that if it ever really came down it, they would be likely to stand up to Arthur in defense of Merlin.
Or at least this applied to 3 out of the 5; Leon had been a knight of Camelot long before Merlin came to Camelot, and had been training and fighting alongside Arthur literally since Arthur was allowed a sword, so Arthur felt safe in assuming Leon's loyalties, and Elyan's loyalty Arthur was certain was his sister's before Arthur or Merlin.
But for the other three, Gwaine, Lancelot, and even Percival, Arthur was under no illusions that they wouldn't come to Merlin's aide if he asked, even if it meant going against the orders of Arthur himself.
Not that Arthur didn't think them loyal to him and Camelot; he knew they was, fiercely so, and they had proven it many times.
But the fact remained that especially Gwaine would abandon Arthur to be at Merlin's side in a heartbeat if it ever became necessary.
And were this anyone else, perhaps Arthur may have been a bit worried about this.
But luckily for everyone involved, this was Merlin. Merlin whose own fierce and utter loyalty and devotion to Arthur inspired all his friends to be so as well.
Merlin, who, Gwaine had informed Arthur once, being loyal to meant being loyal to Arthur above all else, because they all knew Merlin would never forgive any of them if they allowed something to happen to Arthur while they were trying to help him.
Gwaine said he knew this for a fact, because one of the many times they had been attacked by bandits (and seriously, just how many bandits could the woods possibly hide?) Merlin's lucky streak had broken somewhat and he'd been hit. Not too severely, it turned out, but enough that he'd been down and if Gwaine hadn't run the enemy through from behind he probably would have finished Merlin off.
But, Gwaine had grumbled to Arthur later, rather than be grateful Merlin had actually been upset. Because to get to the man that had almost got Merlin in time, Gwaine had turned away from where he was helping Arthur, and this allowed one of the bandits to sneak up behind Arthur.
Merlin had seen it, and promptly yelled Arthur's name while simultaneously grabbing a knife Gwaine had on his belt, and threw it with shocking accuracy to embed it in the bandit's skull.
Merlin himself wasn't able to really explain that shot, except to say it must have been luck and adrenaline.
Later Merlin had apparently told Gwaine to never choose him over Arthur again. Quite firmly.
The bloody self-sacrificing idiot.
Gwaine had agreed whole-heartedly with that when Arthur had muttered as much aloud when Gwaine was telling him the story.
And the real irony of all this? Merlin didn't even fully realize all this. And probably, Arthur thought with a bit of exasperated fondness, would have been upset about it if he had.
4) Merlin was not, in fact, a borderline drunk who spent days at a time in the tavern
OK, so perhaps Arthur had believed it the first time Merlin was supposed to have been in the tavern. Afterall, everyone needed to unwind every once in awhile.
But he knew Merlin well enough to know that Merlin would simply NOT be spending as much time as he supposedly did in the tavern at the expense of his responsibilities.
Arthur had proven this by going to the tavern when Merlin was supposed to have been there, and found Merlin distinctly NOT there.
And to top it off, when Arthur had asked, the bartender had been surprised at the implication that Merlin would be in tavern without either accompanying Arthur or helping a drunk Gwaine.
It was after that that Arthur began to realize that his servant had secrets.
He began to notice when Merlin inexplicably disappeared with no explanation, even some instances he wouldn't have noticed before as they weren't always long periods.
It annoyed him to no end when Gaius would claim Merlin was in the tavern...Arthur couldn't decide whether Gaius was actually brass enough to lie to his king, or whether Merlin was lying to Gaius as well.
But what annoyed him even more was when Merlin simply went along with that explanation, no matter the punishment Arthur would give.
Arthur started to come down harder, hoping that eventually Merlin might admit that he wasn't, in fact, a borderline drunkard and tell him what was ACTUALLY going on to avoid punishment.
But it didn't happen. Merlin simply stuck to his story, every time. And for the life of him, Arthur couldn't figure out why.
Perhaps with anyone else, he may have been afraid of treachery or treason, having his servant going to so much trouble to hide whatever he was REALLY doing.
But this was Merlin, and well, to be blunt, if Merlin wanted Arthur dead or for Camelot to fall, all he'd have had to do was NOT help Arthur one of the many times he'd been injured, or let one of the many poison plots throughout the years actually succeed, or any number of things that Merlin had, instead, helped to stop.
It also helped his case that there were times when Arthur could tell very well that Merlin HATED having to lie to him.
It was Arthur's observations in trying to figure out that mystery that led him to the fifth thing he knew about Merlin.
5) Merlin had magic
It was much too simple once it clicked, and Arthur equal parts wanted to flog himself for not realizing sooner and throw Merlin in the stocks for being so bloody careless.
Because once he realized, it was much, much too obvious. Obvious enough that Arthur wondered how on earth Merlin still had his head.
Then again, he laughed to himself when he remembered that Merlin, years ago, had thrown himself in front of king and court and literally outright told them all that he had magic, and even then had been dismissed.
So maybe Merlin wasn't being such an idiot afterall when he wasn't as careful as perhaps he should have been. And when Arthur sat and went through the memories of the time since Merlin had come to Camelot, he pieced together quite a bit about how Merlin had saved him and Camelot so many times. There were many, many questions still to be answered, of course, but Arthur felt he had pieced together enough to know that Merlin had been doing so much more than he ever got credit for.
But still, Arthur thought that using Magic to clean Arthur's chambers and do some of his chores, which he had caught Merlin at several times now that he was specifically watching Merlin for signs of it (he was not spying on his servant, thank you very much!), was really going a bit far.
So when he was supposed to be doing patrol with some of the guard, but actually purposefully came back to his chambers instead to see what Merlin was up to, and walked in on his clothes folding themselves on his bed and putting themselves away, while Merlin carefully polished his armor, Arthur deliberately slammed the door loudly enough to make Merlin jump.
And jump he did. Merlin jumped about a foot in the air, then all color seemed to drain from his face as Arthur's clothes suddenly stopped their movement.
Arthur raised an eyebrow and crossed his arms. "Merlin." He said calmly, as he indicated the clothes. "Is there something you'd like to tell me?"
Yes, maybe it was cruel, but Arthur really wanted Merlin to tell him himself. And, OK, a slightly evil part of Arthur wanted to see how Merlin would try to get himself out of this one.
And honestly, Merlin was clearly too comfortable with using magic in the relative open, he needed to be more careful. If someone else had caught him...Arthur didn't even want to think of the headache he would have had on his hands.
"I, umm…" Merlin swallowed, glancing from the clothes to Arthur, obviously trying to figure out how to explain it when Arthur had seen it with his own eyes.
"I...I don't know." Merlin said finally. He met his kings eyes, obviously trying to gauge Arthur's reaction. Apparently deciding he couldn't lie or distract his way out of this one, he said slowly, "If...if I did...have something to tell you that is...would I be sent to the pyre?"
Arthur raised an eyebrow and crossed his arms with a huff. "Honestly, Merlin. Using magic to fold my clothes? Are you TRYING to cause me political upheaval? Because what would you have done if someone else had caught you? Tell me, how would it look when my own manservant, loyal to me for almost a decade, was caught using magic? When I was forced to break the strictest law of my own kingdom? It would be one thing if you were revealed by saving the kingdom for all the see, or using it to save my life as you are wont to do...but for such a menial task as folding clothes?! Tell me how that is worth it!"
Merlin blinked. Then stammered, "Arthur...I…" He seemed to read between the lines of what Arthur had said. "Did you...already know?"
"Yes, you idiot. Of course I already knew. You're not exactly the most secretive or stealthy of individuals, Merlin." No need to tell Merlin that of the 10 years they'd known each other, Arthur had only known for the past 2 months.
Merlin's eyes went wide, and he stared at Arthur in shock. "You knew? And you-you didn't say anything?"
Arthur abruptly decided to be honest; afterall, he was hoping that he and Merlin could get everything out in the open here.
"Well, to be truthful I've only know for the past couple months. But now that I know, everything seems so obvious in hindsight. How you survived while my father was king I will never know. But honestly, Merlin...doing magic in plain sight? I suppose I can't say you are going to get yourself killed, because I certainly am not going to execute you, but do you know the trouble it would have caused if it hadn't been me that came in just now? The outrage from some of the council when I refused to have you executed?"
Merlin still seemed to be frozen rigid in shock, and much too pale...like he dearly wanted to bolt from the room but was so petrified he couldn't even do that.
"You - you're not going to execute me?"
Arthur rolled his eyes and threw up his hands. "Yes, Merlin, I am going to execute you. I mean, how horrible of you to save my life and from what I can tell the kingdom many times over. You are certainly evil, and need to be killed immediately."
If possible, Merlin's face went even whiter.
"Oh for heaven's sake, Merlin, I was joking. Of course I'm not going to execute you, you moron."
When Merlin only relaxed very, very slightly, Arthur sighed and sat next to him on the bed. "Merlin."
Merlin just closed his eyes, and didn't turn to look at him, clutching the cloth he had been using to polish the armor very, very tightly.
"Merlin, look at me."
Slowly, Merlin did so.
Arthur placed a hand gently on his shoulder. "I would never see you killed, no matter what the law or anyone else says, Merlin. I swear."
Merlin swallowed. "Banishment?"
Arthur's brow furrowed. "What?"
"Are you going to banish me, then, if you aren't going to kill me?"
For the love of...Arthur wanted to shake him, but stopped himself. It was a legitimate question given the circumstances.
"No, Merlin. I'm not banishing you. You are my friend, I would not see you banished from the kingdom you saved. You are perfectly safe in Camelot as long as I am King."
With that, Merlin seemed to sag into himself, and the cloth fell from his hands and for one horrible moment Arthur thought Merlin was going to cry, and he had no idea what to do in that situation.
But then Merlin took a breath, then another, visibly calming himself down before he managed a tremulous smile at Arthur. "I...thank you." He breathed.
Arthur nodded. "You're welcome."
Merlin gave a shaky laugh. "I'm sorry. It's just...you have no idea how much I have both been terrified of and wished for this day."
"I can well imagine."
Merlin gave a true smile then, eyes shining. "So. Arthur. I have magic."
Arthur rolled his eyes. "Yes, I think we established that I know that."
"I was born with it. I didn't choose it or anything. And apparently, prat, it was meant for you."
And thus started a conversation that lasted the entire night and most of the next day, where Arthur then learned ALL of Merlin's secrets.