It is apt, given that this curious gem of a documentary is about a city that no longer exists, that it should itself have vanished from the radar for years until its release on DVD in 2008 with Les Bicyclettes De Belsize.
Alluded to by writers, artists and musicians more often than it was actually seen, its absence has magnified its status as a cult artefact. Presented by a tweedy James Mason whose self-consciously sardonic demeanour conceals an awesome awkwardness when called upon to interact with the hoi polloi, The London Nobody Knows is an unusual example of a documentary in which the flaws are at least as fascinating as the historical footage.
Over a brisk 53 minutes Mason visits Camden's derelict Bedford Theatre music hall, where the artist Walter Sickert once listened to Dr Crippen's wife sing. In the Holborn gents - a proud example of Victorian design - Mason recounts the story of an attendant who kept goldfish in the cistern. "Here you find the only true democracy," notes Mason with the sniffy air of a man unlikely to be caught short after a night on the sauce. "All men are equal in the eyes of a lavatory attendant."
These observations aren't necessarily Mason's own: The London Nobody Knows is based on the work of author, artist and life-long London obsessive Geoffrey S Fletcher, a pioneer of the sort of psychogeographical speculation associated with writers Iain Sinclair and Peter Ayckroyd.
Director Norman Cohen, who would go on to make the Spike Milligan adaptation Adolf Hitler - My Part In His Downfall and a couple of Confessions films, intersperses Mason's monologue with footage of market traders, meths drinkers, buskers and labourers. There's a sense of melancholy anonymity to this footage which makes much of the film oddly contemporary: the sight of flailing, meths-ed up boozers scrapping on the street has the feel of an eerie art installation. In 1967 London's beautiful people may have been swinging through Chelsea, but here the city and its residents are worn-out through over use and knackered by the changes being wrought upon them.
It's when Mason drops the urbane urban adventurer act to interview down and outs housed by the Salvation Army that the film evolves into a fascinatingly anachronistic exercise in reportage. In his mellifluous, perfectly modulated tones, he asks some of the East End's homeless how they got that way, and invites himself into a house in Spitalfields to examine the site of one of the Ripper murders. You half expect - and perhaps Mason does too - to see the locals doff their caps to the toff.
Like Patrick Keiller's magnificent London made 27 years later, this is a film about the city in an acute period of change. Sometimes it's suspicious of this. Mason has little time for the new brutalist developments rising over the river, but it also accepts that the project of London is never really finished. When audiences no longer turn up at the Bedford Theatre, says Mason, it's only right to call for the wreckers.
From our perspective in the twenty-first century, what The London Nobody Knows presents is an opportunity to be nostalgic about nostalgia itself: here is a film that looks back at the past from a point in history which has itself been erased. That lends it a poignancy which might been less apparent in 1967. As a social history lesson, a snapshot of street life and an imaginative documentary it's a wonderful little record. They don't make memories like these anymore.