A while ago I received an invitation from something called an 'Independent Seminar on the Open Society', in reality the Adam Smith Institute, the free-market fundamentalists.

This particular seminar was entitled 'The Economic and Political Landscape for the Next Generation', and it would be aimed at Sixth Form school students. Aping Parliament and university debating societies, there would be a motion: 'This House would prefer to be led by the invisible hand' - the image used during the 18th century Scottish Enlightenment by the supposed founding father of free-market economics, Adam Smith. Would I like to oppose the motion?

Well, I do. In the spirit of open debate, and despite the paltry seven-minute slot on offer, I agreed to make the trek to London from the fastness of my Dutch barge in Bristol.

So I arrive at one of those disused religious edifices, now a conference centre set among government offices in the heart of Westminster. It is clear, from the names of London's leafier suburbs on the coaches parked outside, that 'Sixth Formers' means public (in Britain, of course, private) schools, which are still preparing their precious heirs for power.

I arrive just in time to catch the tail end of a speech by the louche Liberal Democrat MP, one Lembit Opic. He is draped against a lectern, telling some 200 youths that 'you get the government you deserve'. Can he mean the expenses scandal that has engulfed the Houses of Parliament? Their 'invisible hands' have, like all the others, been in the till. As the hall empties after his speech, Opic takes a harmonica from his pocket and blows a few artless riffs into the microphone.

My own gig is the slot after lunch when bored teenagers are inclined to nod off. Proposing the motion is a crisp young student from the London School of Economics; seconding, a willowy figure from Oxford billed as the 'World Debating Champion'. They both wear suits.

Opposing the motion (with me, and a little more casually) is Chris Harman, the veteran Socialist Workers' Party ideologue, whose most recent book is Zombie Capitalism. He can recall that I was once charged by the SWP (via the celebrated journalist, the late Paul Foot) with being an undercover agent of MI5. Not an easy charge to rebut; but then, any self-respecting revolutionary group requires at least one infiltrator. Both of us are, shall we say, over 60. All four of us are male.

So reactionary youth has been set up to savage radical experience, in a reversal I know is untypical of the times. We get underway with a show of hands by the audience – heavily for the motion.

The proposer outlines the miraculous symmetry of free-market economics for beginners. Chris Harman launches an unreconstructed assault on capitalism. The willowy World Champion berates such 'clichés of the 1970s' and blames the financial meltdown on governments. I berate such 'clichés of the 1930s', with a hint at the virtues of co-operation.

Questions from the floor are preoccupied with Russia. The general drift favours the individual against the state, as if the Cold War had never ended. Another show of hands: even more for the motion - without, of course, counting the invisible ones.

Outside, a balmy autumn afternoon in London. I head for my old territory in the much-reviled Hackney. I sit and wait for a friend in disbelief, sipping a cappuccino in the open air, beneath the canopy of a new library building. Across the square HACKNEY EMPIRE is carved in clean, blockbuster stone lettering on the roof of the salvaged music hall.

A text message says my friend is trapped on a bus in a motionless sea of traffic. When she arrives, cursing London darkly, we repair to a bar with sofas and order Campari – the first the bar tender has ever served. We speculate about the succeeding generations of innocent young recruits to the point of view of the SWP or the Adam Smith Institute. The former tend, I fear, to get lost - the latter never to get quite as rich as they would like.

My unfortunate friend has been the victim of a fire. She is all but destitute. To my astonishment, she feels 'free at last!' - and the local council has taken some sort of care of her. She puts me on a bus she says is for the city centre, but it goes the other way.

On the train back to Bristol I don't at first pay much attention to a white-haired gent sitting opposite me. He fidgets with an old book and, from time to time, whistles. Why is this faintly familiar to me? Neither of us catches the other's eye.

A while later he phones for a taxi to pick him up at his distination, and speaks his name. Good lord! It's him, an old college acquaintance, now a rather grand journalist. I'm about to greet him when something stops me. I failed to recognise him before he spoke his name. I'll wait a while, maybe make that a little less obvious.

But then, he hasn't recognised me either. Or perhaps he has. Perhaps, truth to tell, neither of us much wishes to be re-acquainted. I'm still mulling this over when he gets up, dons a felt hat and, with a whistle, vanishes.