IN 1902, fired up by his triumphant retrievals from the wilderness of the Yukon, the author-adventurer Jack London set out, as a special kind of tourist — courtesy of Thomas Cook — to compile an impassioned despatch from London’s lower depths.

Everything about The People of the Abyss, now reissued at a moment when the metropolis is again brutally divided between quantums of wealth and indigence, is dynamic, driven, challenging.

Here is social polemic as a wolf-pack saga.

Here is a vivid text to demonstrate the fault lines of what we are presently experiencing: empty Babylonian towers of spectacular hubris overshadowing rough sleepers, who must remain invisible under foot, or find themselves banished to hobo camps under motorway spurs, treated to one-way-tickets to dying seaside resorts.

The author-as-detective presents his descent into elective poverty as a pre-Orwellian fugue, a sleepwalker’s nightmare journey through reeking underclass sets out of Henry Mayhew, Arthur Morrison and Blanchard Jerrold, with apocalyptic engravings by Dore: reportage as a form of science fiction.

Feisty Jack is a time traveller, a visitor from a newer, cleaner, go-getting, meat-eating civilisation.

He witnesses the pomp and ceremony of the coronation of Edward VII and is appalled.

In every way, he is the wrong kind of temporary immigrant.

The one who looks and listens and asks questions. The one with a notebook.

It is uncanny how The People of the Abyss anticipates later figures with rucksacks, writers whose reputations were made by waxing lyrical over periods of life among the “fellaheen.”

London summons Jack Kerouac, 50 years before his compatriot’s most famous book is published, by zooming in on the term used for vagabondage in the United States: “on the road.”

Wandering east through this city, as he reports in Lonesome Traveller, Kerouac gets no further than St Paul’s Cathedral.

The London under investigation is unstable.

It’s a labyrinth, a maelstrom. An abyss.

It is also a city twice divided: first by the liquid spine of the Thames and then by the terrible shadow-line between west and east, respectability and survivalism.

Those who live on their dividends in bright airy places and those who scavenge for coins to keep themselves alive, one day at a time.

The People of the Abyss is intentionally shocking: the regimented horrors of the workhouse, sickness, exploitation, overcrowding, disease, premature death.

And all of these ameliorated by the fug of drink.

Much of Jack London’s material, factored like sensational fiction, is supported by blocks of statistics, newspaper cuttings, court reports.

The man from San Francisco crosses paths with Thomas Holmes, the criminologist and missionary who compiled London’s Underworld, which was first published in 1912.

And, as with the original version of the Holmes book, early editions of The People of the Abyss, issued by Isbister and Company, came with hard evidence in the form of uncredited photographs.

Reality is pressured until it becomes fantastic, grotesque. Jack London, trusting to native guides, hardened policemen, fellow socialists, is describing a parallel world.

The people he encounters are Morlocks, creatures denied the light. They are as sullen and defeated as the deformed subterraneans depicted by HG Wells.

London is at pains to present himself as a sturdy Yankee, undeceived, physically stronger, taller, hungrier than the subdued creatures of the depths he encounters.

Along with controlled fury at the injustices of this cold and materialist gulag, there is a strain of the eugenicist in this mediated response: sweep it all away.

The sickness of defeat. The ancient races scavenging for life beyond their strength.

Our investigator speaks of “a woman, of the finest grade of the English working-class, with numerous evidences of refinement, being slowly engulfed by that noisome and rotten ride of humanity which the powers that be are pouring eastward out of London Town.”

The narrative power of London’s account derives from its essence as performed fiction, a documentary novel. Discrete episodes are shaped, articulated, dramatised: remembered or constructed conversations, extreme characters, the architecture of control and submission.

As a key text in London literature, The People of the Abyss hovers between the alchemical metaphors of dust and water in Our Mutual Friend (1864-5) by Charles Dickens and the neurotic shifts between pornography and paranoia, centre and suburb, in Joseph Conrad’s The Secret Agent (1907).

Everything Jack London achieves in his season in hell, when he is disguised in borrowed rags, moving with a sailor’s swagger, plays against the chilling witness of the photographs.

And the measure of what he leaves for contemporary readers is that the integrity of the account is not diminished by what we are shown: the people muted by the camera’s oblique interrogation, the overcrowded rooms, the Monster Doss House, the shame of the streets. “The fear of the crowd smote me. It was like the fear of the sea.”

The People of the Abysss, with original photographic plates, is published by Tangerine Press, price £15.