It must be one of the world's spookiest cycle rides. I pedalled through eerily deserted streets that once pulsated with thousands of scurrying feet. I passed empty glass-fronted shells that were, within living memory, noisy hubs where prosperous citizens feasted, boozed and traded. Heroically tall buildings, testimony to the improbable triumph of engineering over soft clay, still dominated the vista. Indeed, the lights were still on in many of them. But was anyone at home? I felt like the man on the first page of John Wyndham's The Day of the Triffids - the chap who wakes up one Wednesday in the middle of a big city ... and hears no traffic.

This was a ghost town I was crossing. Its glinting towers suggested that it was once the heart of a great civilisation. But the heart had stopped beating. The people had fled. At some undetermined moment in history, someone somewhere had turned off a gigantic life-support machine, and this once teeming metropolis quietly died. Or so it seemed.

Where was I? On some epic cycle ride through the ruins of the Incas? Hitting the tourist trail in Pompeii? No, this was London, last week. On impulse last Thursday morning I took my trusty Claud Butler on a mini-tour of Europe's two greatest financial heartlands: the Square Mile and its upstart rival, Canary Wharf. It was the most disquieting sightseeing I've done for years.

Agreed, it was cold. Granted, it was only seven days after new year. Perhaps many people were still on an extraordinarily extended Christmas break. But if that was the case, doesn't it tell us something? Who ever heard of those mighty temples to Mammon hibernating for three weeks? Since when did the world's most resolutely avaricious barrow-boys and pinstripes allow a few mornings of sub-zero temperatures to deflect them from their daily grind of earning zillions for their clients and themselves?

No, this wasn't some unusually prolonged midwinter snooze. It seemed very much like the last rites of a way of life, and of the vast supporting cast of bars and nosheries, dry-cleaners and cabbies, florists and hairdressers, that sprang up to service it. I've been cycling through London since I was a schoolboy, back in the middle of the last century. I've never known a mood like this. The city that stood battered but resolute through the Blitz has finally had the stuffing knocked out of it - not by bombs, but by some obscure global financial chicanery that nobody can really understand or control.

How swiftly, how viciously, the wheel of fortune turns! The last time that I took a sociological bike-ride through London, five years ago, I found myself standing beside what was then the Millennium Dome - empty, barricaded, desolate and seemingly useless - and looking across the Thames to the bright lights of Canary Wharf: a beacon (it then seemed) of capitalism at its most smug, rampant and impregnable. As readers with elephantine memories may recall, this juxtaposition moved me to make several tart observations contrasting the fortunes of insanely unnecessary, obscenely subsidised white elephants with the self-supporting triumphs of London's financial heartland.

Good grief, what a turnaround! Today, the Dome, renamed the O2, has miraculously transformed itself from the nation's lamest duck into its grandest palace of varieties. By savage contrast, Canary Wharf totters on the abyss of impotence and humiliation; its vast trading floors metaphorically propped up by dollops of taxpayers' money several hundred times larger than all the subsidy ever poured into the Dome.

Stalin once observed that one death is a tragedy, but a million deaths is a statistic. (That was lucky for him!) It's much the same when one looks at the soaring unemployment figures, or the grotesque level of debt that will cripple this country for a generation. The numbers register on the brain, but not the human wreckage that they signify. It's only when you start chatting to a Woolies shelf-stacker queueing in quiet despair at the Jobcentre - or wander, as I did, through desolate city streets energised only by the mounting desperation of the traders still clinging to solvency by their fingertips - that you can get any measure of the depth or width of this catastrophe.

How will it end? And where will it end? Will the ripples of this disaster spread outwards from Manhattan and London and suck everyone and everything into its incomprehensible vortex? If you read some financial “experts” (and no financial “expert” escapes ironic quotation marks these days), you would be forgiven for believing that this crisis won't be over until every job in Britain has disappeared and every home has been repossessed.

Oddly, though, when you talk to real people, especially outside London, the mood is more sanguine and stoic. Some businesses are struggling; some are doing tolerably well. Life is tough, and sometimes made tougher by the ineptitude and greed of metropolitan movers and shakers - but ordinary people tough it out. They have no choice.

It's a tale of two poems. Cycling round London last week, two thunderous lines of verse came to mind. “My name is Ozymandias, king of kings: Look on my works, ye Mighty, and despair!” That was the inscription Shelley imagined being found on the sole remaining ruins of a once glorious empire. It's a gloomy thought - that all civic ambition is hubris, and every civilisation doomed to crumble to dust - but I felt it echoing ominously round London's empty streets last week.

But when I go into the regions, far from the madding crowd of bewildered bankers and media panic-mongers, the poem that comes to mind is In Time of “The Breaking of Nations” - the three-stanza masterpiece that Thomas Hardy wrote as Europe tore itself apart in 1915. In it he observes the old farmer with his plough, the maid whispering sweet nothings to her lover - in other words, the eternal, steady, phlegmatic plod of country life - and promises us that “this will go onward the same, though Dynasties pass”.

Let's hope he is right. We have certainly witnessed the passing of a few dynasties in the past few months.

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