Occasionally (very, very occasionally, mind), John can understand why Sherlock hates sleep so much.

He's never been much of an intellectual, himself. He's clever, that much is a given for getting through medical school, but he's always been more of a 'doing' man. Hence the career move to the army, where the application of his knowledge makes an immediate difference, where it can save a man's life right in front of his eyes. Trying in vain to diagnose 'flu over the telephone just doesn't have the same feeling to it.

Thus, he is quite able to disconnect from the intellectual and concentrate on the physical. Though he's never really thought about it before – never in fact had reason to do so – this is probably why he's never had problems in getting to sleep. Nightmares once asleep are a different matter, but there has always been a slight sense of satisfaction and relief in knowing that it only takes him a perfectly average seven minutes to fall asleep once more, once his mind has let go. It always does.

Or it always used to. Before he was shot, before he returned to a place he had once felt was his entire world and now seemed to be a prison cell (London always seemed to be just as grey as the interior of any police station), and certainly before he met Sherlock Holmes.

For the first few days or weeks or month, he assumes that Sherlock does sleep, but that he just doesn't do it at conventional times. Wasn't it Da Vinci who only slept in twenty minute bursts? Polyphasic sleep, that was the technical name for the condition or system or schedule, known in some circles as the sleep of genius.

It takes him a while to realise that there is simply no way that this can apply to his most unorthodox flatmate.

Every time John is out of the flat, he comes back to find Sherlock with a nicotine patch. Something to do with needing some sort of stimulation, and if that can't come from conversation with John or the skull (which John has immediately nicknamed Yorick), it has to come from more conventional stimulants.

Nicotine: causes a release of glucose from the liver and adrenaline from the adrenal gland. Not exactly conducive to falling asleep.

Surely, then, he is sleeping at night, but for a lesser time period than the average adult male and, let's face it, Sherlock is not your average adult male.

Yet this, too, is an impossible hypothesis, because John's own broken nights give him plenty of evidence to suggest that Sherlock much prefers to use the night hours for his own, intellectual purposes. The physical need for sleep seems to be…

Completely ignored.

But that's ridiculous! If a person doesn't sleep, he dies. A little known fact, but as a doctor, John has learnt about fatal familial insomnia. This is the only case in which a person can refrain from sleep entirely. And death occurs within thirty six months.

A cyberchondriac might become hysterical upon Wikapedia-ing this little known condition, but John isn't concerned. He knows there are many other symptoms that present: paranoia, panic attacks, hallucinations, chronic weight loss, dementia, muteness and unresponsiveness. Whilst several of these could arguably be applied to Sherlock, John knows him well enough to know that they are merely affectations. Sherlock is verbose enough when he has something to say, and is only so deceptively fragile-looking because he refuses to eat whilst on a case.

It's this train of thought that first leads John to believe that the lack of sleep must also be achieved deliberately and sustained only through microsleep.

At first glance, this theory seems rather ludicrous. Why on earth would Sherlock harm his precious brain in such a way? Insomnia causes a lack of concentration; even Sherlock cannot be ignorant of that.

And yet… It's one of Sherlock's favourite phrases, or perhaps it's a motto: When you have eliminated the impossible, whatever remains, however improbable, must be the truth.

Which is all very well and good, and perhaps Sherlock's methods of deduction might not be impossible for the general public at all, but why? The question remains lodged in John's mind, buzzing with all the persistency of Sherlock's constant text messages. It's this that makes him turn once again to playing the detective, watching Sherlock even more closely than he has before. Sure enough, he starts to notice the split seconds where Sherlock succumbs to sleep. The signs are less obvious in him than they are in most – no balance issues, and his remarkable mind catches him up on what has been said without issue – but there are tiny things that only the most observant man would see. John wonders that Mycroft hasn't mentioned it before.

The most prominent sign that Sherlock is asleep, rather than blinking or zoning out or even doing nothing at all, is the facial expression. In all the time John has spent in Sherlock's company, he has rarely seen Sherlock's expression completely unguarded. Even in discussing the most trivial things, there is an air of complete control about Sherlock. The obvious exceptions occur when they are in the midst of a case, and the mental invigoration overcomes any conscious thought that he might need to adapt his behaviour in accordance with the company.

When Sherlock lapses into sleep, however, he loses that guardedness. He becomes, for a tenth of a second, vulnerable. John finds himself utterly fascinated by this. He has seen uncontrolled intense concentration, uncontrolled frustration and uncontrolled glee, but he has never seen Sherlock simply uncontrolled. The concept almost seems nonsensical, paradoxical. The actuality is… well, if it were anyone else, it would probably be endearing. When applied to Sherlock, however, it's actually quite worrying.

John has long since learned that if anything can be considered normal, it cannot be considered normal for Sherlock. Example: using nicotine patches is healthier than smoking. Example number two: exercise is good for you. Example number three: people understand the concepts of personal space, both literal and metaphorical. As a doctor, he's already trying to avoid palpitations at the thought of the cocaine he knows is hidden somewhere in the bathroom (he hasn't yet found/flushed it), the refusal to eat whilst on a case, the frightening amounts of caffeine and nicotine that Sherlock imbibes on a daily basis. And, as a doctor, he's spent many an hour arguing with Sherlock over these subjects, and many an hour trying to rectify the problems without arguments.

He is now fairly certain that Sherlock is cutting down on the drugs. Possibly because he knows John will report his hiding places to Lestrade for all those drug busts if he finds them. Even for the great Sherlock Holmes, there are only so many hiding places in one small flat. A few well-meaning texts from Mycroft have informed him of the few foods Sherlock might deign to ingest (apparently the sugar kick from American pop tarts is more beneficial than the necessary digestion is detrimental) and by making sure that the kitchen is well-stocked with these as well as human body parts, he gently encourages Sherlock to eat a little, if by no means healthily or enough. As for the caffeine, he has tried buying decaf, but Sherlock had suddenly needed to use it in order to ascertain if it could be used in the manufacture of a certain poison. John had got the hint.

Sleep, therefore, is merely the next frontier in what has become the battle to keep Sherlock alive.

Blimey, that would make a good blog title.

Getting Sherlock to sleep, however, is more difficult than making him eat. For one thing, Sherlock is utterly convinced that he doesn't need it. He can accept his body's need for food, having collapsed from hunger several times (only once since John has moved in) but his microsleeps serve him perfectly well, or so he thinks.

To start with, John tries to explain how dangerous this is. He cites the hundreds of car accidents that occur as a result of drivers falling asleep at the wheel; Sherlock simply responds that he doesn't drive. John tries to persuade him that it could prove perilous in the midst of one of his frequent chases across London; Sherlock simply says "adrenaline". The scathing tone of voice, implying that a doctor should know this, makes John switch tack. He reminds Sherlock that microsleeping cannot refresh the body or, more importantly to him, the mind. Sherlock argues that his mind doesn't need refreshing, but it's John's turn to raise an eyebrow.

"Just try it," he suggests. "You might be surprised."

"I have," Sherlock informs him. "I didn't like it."

John doesn't repeat you didn't like it, because he knows how much Sherlock hates it when people do that. Instead, he just asks, "Why? Nightmares?"

"Don't be ridiculous, I'm a sociopath." It's a mark of Sherlock's respect for John that he doesn't go into exactly why that would preclude nightmares from affecting him.

"You know sociopathy isn't medically recognised any more," John says, distracted despite his mission.

"APD sounds dull," Sherlock retorts.

John can both expect and agree with that objection, so he gets back to the point. "So why don't you like sleeping, then?"

There is a short pause, and John thinks Sherlock might have sunk back into his thoughts, submerged once again. He almost throws up his hands and turns away, until Sherlock explodes off the sofa, almost literally explodes in a blast of sudden energy, ending up just slightly too close to John.

"Sleep is boring and it's a waste of time," he begins, and John would argue if he weren't so taken aback. "My mind is constantly going; I don't stop thinking. The energy of it, John, the sheer excitement of it—you don't understand. You can't possibly feel the same mental invigoration. Don't argue, I know you don't."

Suddenly he is whirling away, tearing away from John with his arms uplifted. He looks like a dancer or a madman or both.

"How can I give this up?" he demands. "How do I let this go? Answer: I don't."

He comes to an abrupt halt, staring intently at John from across the room, as though trying to telepathically show John the inferno that is his mind.

The fire in his eyes subsides.

"That's why I don't like to sleep."

Throughout this performance, John has remained still and staring. This is how they are, he recognises. He is the calm to Sherlock's storm. Now, he wonders hwo on earth he is supposed to respond to that, before realising that there is only one way to do so. The only thing to do is to pretend that he had received a perfectly normal response with no added drama.

Calm the storm, he thinks.

"Well, from a medical point of view, I still feel obliged to point out that perhaps your brain would function better—" he resists the temptation to say 'even better' "—if it was well refreshed."

Sherlock's less than eloquent response is to snort and collapse back onto the sofa.

"Just try it," John says again. "Just for one night, just to humour me. Go on."

"Did you not listen to a word of what I just said? I can't just switch off like everyone else."

If anyone else had made this statement, it might be tinged with envy or regret. Voiced by Sherlock, it is merely scathing. John ignores the habitual scorn towards the rest of humanity and comes to sit on the unoccupied half of the sofa.

"Have you never tried counting sheep?" he suggests.

"Too distracting. The sheep refuse to march past in an orderly line."

John is briefly surprised at this. Control freak Sherlock not in control of some imaginary farmyard animals. He wonders if he could conclude that Sherlock cannot control his own mind, and that this is why he's a control freak in the first place.

"Stop analysing me, you know it annoys me."

He certainly does, and an annoyed Sherlock is almost as bad as a bored Sherlock.

"Okay, how about a ticking clock?" he suggests.

"Too regular; it doesn't keep my interest."

It's because of this that John ends up in bed with a sociopath. Apparently his fluctuating heartbeat is interesting enough not to bore him but not distracting enough to prevent sleep. Sherlock deems the situation rather soothing.

John cannot agree.

"Do you realise that your heartbeat is far too high for a fit man in a resting state?" Sherlock murmurs.

"Yes, well, I'm not really used to trying to sleep with you lying on my chest."

And indeed Sherlock is sprawled over most of John's torso, surprisingly heavy for such a slim man, his ear pressed over John's apparently frantic heart. Sherlock's breath as he speaks flutters against John's t-shirt; he seems utterly comfortable being this ridiculously close to his flatmate.

Suddenly, John really hopes Mrs Hudson won't randomly appear in his room.

"It just spiked again," Sherlock informs him.

"Thank you for that piece of information, but isn't the point of this exercise supposed to be you getting some sleep?"

"Don't state the obvious," comes the predictable response, along with a less predictable jab in the stomach.

"Ow! Stop that or I'm kicking you out."

"I'd rather you didn't."

"Well don't poke me, then."

Sherlock doesn't answer, and John takes that as an agreement.

They lapse into awkward silence. At least, it feels awkward to John. Still, he doggedly lets it be, determined not to show his discomfort any further than he can help, given who is lying on top of him.

The minutes tick by. Occasionally John has an urge to turn his head to look at his glowing bedside clock, but he doesn't want to disturb Sherlock, who is probably really struggling to—

Wait. Did he just snore?

John almost stops breathing himself as he listens carefully to the little snuffling breaths shivering over his chest, and sure enough, they are deeper and further apart than they were.

Sherlock Holmes, chronic insomniac, is asleep.

A wave of triumph sweeps through John; it's a warmth that's almost physical. He has won in this latest battle for Sherlock's health. He has made a difference.

John has had far too many therapy sessions to be unaware that he has a bit of an inferiority complex when it comes to Sherlock, though he defies anyone to keep their ego intact with the world's only consulting detective around. But right at this moment in time, he is the winner, he has control, and Sherlock is reduced to a mere man as he sleeps.

And for the first time, John thinks he might understand just a part of why Sherlock hates sleep so much, because why on earth would he want to close his eyes and shut off his mind now? In fact, he's not sure it would even be possible to disengage.

Perhaps it's disturbing that only Sherlock is cause enough for John to be unable to switch off. Actually, it's definitely disturbing. But that's something to be considered in the cold light of day. For tonight, John is just going to enjoy his night of stolen insomnia.