It was never going to be a good day, thought Vernon Dursley as he attempted to balance a steel pot of tea, a Chelsea bun and a plate of egg sandwiches on the wholly inadequate, shoddy plastic tray provided by the King's Cross station café. Having to waste a nice, normal summer day picking up his delinquent nephew on pain of dire retribution was bad enough. But the rest seemed uncalled for, somehow. Yet another sign that the country was going to the dogs, of that there was no doubt.

It had all began innocently enough the previous night, with a nice, civilised dinner of home-made seafood delicacies at the home of his sister Marge. They had spent a delightful evening discussing house prices, immigration quotas, the iniquitous bus lane situation in the town centre and the general decline in standards up and down the land. Unfortunately, on their return home both he and Petunia had been prostrated with violent stomach upsets. Petunia – always a sensitive plant, ha ha – had been hardest hit, and by the time they had to leave it was plain that she was in no condition to go anywhere, dire retribution or no dire retribution.

Then Vernon had realised that his son had taken the Volvo without asking – out carousing with those awful new friends of his, no doubt. He had been forced to take Petunia's little metallic blue runabout, which had left him at a most humiliating disadvantage against the yobboes you meet on the roads these days, and the steering wheel which was far too close to the driver's seat had left a painful welt on his stomach.

And now the wretched café was full. Every table had someone sitting at it: a pair of students discussing a trip to Thailand (national service would soon knock them into shape), an elderly couple holding hands over a pot of tea (disgusting at their age), an academic-looking woman poring over a thick textbook (probably can't find a husband, and no wonder), a younger woman with dyed hair fussing over a baby in a pram (they just do it to get council flats, you know) and three bikers in full leather regalia (unspeakable).

But one table in the far corner was occupied by a respectable-looking lady of about his own age, clutching her handbag to her chest and looking around her with huge, nervous eyes. She was about Petunia's age, with similar colouring, but plump and round-eyed where Petunia was lean, and dressed in the kind of clothes his wife had favoured in the heady days of their courtship: pleated skirt, white blouse with a tie neck and elegant but sensible shoes with bows on the toes. In short, the only other respectable person in the whole beastly place. That settled it. He adjusted his grip on the tray and picked his way fastidiously across the steamy, crowded room.

He almost made it across the room without further loss of dignity, until he skidded on the baby's discarded rattle, and only just managed to stagger into the corner table's other seat, splashing tea all over his Chelsea bun and dropping his wallet onto the oily floor. As Vernon was gasping with indignation and brushing crumbs of egg from his suit, he noticed the lady leaning across the table towards him.

"Excuse me… Your wallet," she said in a low, timid voice as she handed him his wallet, which had landed open, exposing an impressive set of credit cards and a couple of smiling photographs of his family.

"And what a fine, strapping young man!" she added admiringly, looking a picture of Dudley on his first day at Smeltings, brandishing his Smeltings stick at the camera. "You must be very proud."

Vernon looked bleakly at his son, who at the age of eleven had been all he had ever wanted. There was a lump in his throat. The woman opposite him must have seen something in his eyes, for sighed and said ruefully:

"Ah, but they're so much easier when they're that age, aren't they?"

Looking back on that day, Vernon Dursley could only attribute his sudden, unlikely garrulousness to the lingering effects of his sister's paella, but once he started talking the floodgates opened and he found himself unable to stop. He found himself telling this stranger how he and Petunia had placed all their hopes on their charming, talented son; the sacrifices they had made to send him to the best school to avoid him picking up low habits from the local yobboes; their dawning, horrified realisation that the associates he had chosen for himself at school were leading him into habits every bit as bad. The rest spoke for itself: the dyed black hair with disturbingly shaved patches; the obsessions with skulls, black magic and death; the wild-eyed, frightening louts who had seduced their precious boy into bad living; the posters of pale, androgynous figures in disturbing poses; the odd smells drifting from his room; the unsociable hours; the ludicrous clothes, rattling with chains or daubed with horrible emblems; the awful tattoo that had had Petunia crying herself to sleep every night for a week…

Finally, Vernon talked himself to a standstill. He looked up, as near to self-conscious as he ever came, to find the woman staring at him, her round blue eyes swimming with tears. Timidly, she reached out and patted his hand with plump, beringed fingers.

"Oh, I know," she said. "It's just so beastly! These poor boys… when will it all end? My Cecil's just the same – after his father had to… well, go away to help the Ministry with some questions I thought he'd be safer at school, but it's just made everything worse! I fear for him, really I do – these people just aren't safe. And that wretched Headmaster – worse than useless – I really feel he's let poor Cecil down…"

She paused, overcome, dabbing her eyes with a lacy handkerchief.

"My dear Mrs…" said Vernon, made uneasy by the display, yet at the same time strangely comforted by the knowledge that he was not alone.

"Warrington," said the lady with a dainty sniffle. "Delia Warrington."

"Vernon Dursley," he replied, offering his hand. They shook hands briefly, and then Vernon launched into one of his favourite subjects: All Teachers Are Thick; All Headmasters Are Thick. After twenty minutes in which they roundly abused all members of the educational profession as insensitive clodhoppers incapable of recognising real talent, and deplored the declining standards of the age, both of them were feeling much better.

Finally, Mrs Warrington glanced up at the clock on the wall, sighed and gathered together her things.

"Well, I'd better be going," she said. "Poor Cecil will be arriving any minute now. Thank you so much for listening – it's been such a comfort. And I'll be thinking of you and your boy, and wishing you both all the very best. We just have to keep hoping, don't we?"

This was the moment Vernon had been dreading. His wretched nephew's train would be here any minute – how was he going to get to it and at the same time avoid the humiliation of being seen by this charming woman waiting alongside that bunch of freaks, degenerates and misfits?

Once they were back in the crowded main concourse, Mrs Warrington turned to him again.

"Your shoelace, Mr Dursley! Do be careful – loose laces can be so dangerous!"

Sure enough, his lace was loose, and he bent down to retie it. When he stood up again, Mrs Warrington had disappeared into the crowd. Disappointed, but also secretly relieved, Vernon Dursley shrugged his massive shoulders and began to shove his way through the crowds to Platform Nine.

And that was the last he saw of Delia Warrington. Just for a moment, as his awful nephew came out from… wherever he'd been (not that he wanted to know), he thought he might have caught a glimpse of her among the waiting parents. But that was plainly impossible, he told himself sternly: such a nice, respectable woman would never be seen dead in such company.