First Person: The heat is on: Anarchy takes hold as the temperatures rise

For all the world, I'm glad I didn't miss this. Five minutes later out of the office and he would never have come, briefly, into my world. But there he is, stepping into my carriage, the last carriage, on this Northern Line train, southbound at Bank. And it is only 8.15pm.

His suit is sober, if double-breasted. Blue. He's reading a book, Picador, Cormac McCarthy, held in his left hand. His hair ruffled, a little bit Brideshead. And in his right hand, a glass of white wine. One of those straight-sided pub tumblers.

And, oh the pleasure of it, he casually puts the glass on the seat next to him, as if it were a table and he were at home. And goes back to his reading. Does he look at the glass as the train moves off? Does he glance up to see if anyone has noticed?

Well the guard has noticed; looks, first at the glass, then at the man reading in the blue suit. The glass now occupies the seat where the guard had been sitting. The guard, anxiety creasing his features, hair sweated, tangled, puts up his rail, separates himself off from the rest of us, pulls out his special guard seat. And sits down.

The train jerks, the reading man glances momentarily at his glass, then goes back to his reading. At intervals he sips. He is, most definitely, not on a train but at home already, and does not see my helpless grin, which the guard, staring straight through us crazies, resists sharing.

There is, of course, a simple reason why this thirtysomething broker is doing what down-and-outs do clutching cider in brown paper bags and hard lads do with tall blue cans of Tennents. He is boozing on the Tube because this is a heatwave. And, as in any self-respecting ritual, the normal order of things must be temporarily inverted, the way that, at office parties, bosses are insulted by their minions, or their minions become so nice to each other that they end up in back rooms together. Only thus can the boss's normal gravitas and workday chastity of the office be preserved.

All this, naturally, my man is aware of, as he gets down to his last centimetre of plonk and I get off, wondering if he'll take his glass back to the pub in the morning. He is drinking on the Northern Line in a heatwave just to show that, in the normal course of British things, brokers don't do that.

Once out of the train I begin to wonder who will be next to send normality hurtling to the border. The newsagent's looks the same as ever, with its original and non-ironic 'Smoking Kills poster next to the cigarettes. I suppose having the blow-heater on is a bit strange, but not in the same league as brokers sipping spritzers on the Northern Line.

Outside the shop, and in defiance of any known current or planned EU directive, a Vauxhall Astra minicab is sousing the balmy air with an extraordinary wall of thick, grey semi-combusted ordure, through which, with the rapidity of an aircraft slicing through clouds, my bus plunges, trailing children from the open platform.

But I'm no longer impressed. London is descending to normal levels of anarchy. Even the temperature has dropped. Yet when I get home, I see that the family on the ground floor of my block have waited for this disjointed moment to do away with their regulation blue front door. In its place stands the proud gateway to a dream: the first Persil-white, vinyl-smooth neo-Georgian porch on the estate. It was a short heatwave, but some things would never be quite the same again.