I am in a tunnel, a hundred feet beneath the Euston Road. This used to be part of the London Underground before it was closed off and abandoned sixty years ago. Now it is used for storage and the occasional TV production whenever an eerie version of the Tube is required. As in any Underground station, the walls are lined with posters. These ones terminate abruptly in 1962. There are adverts for West Side Story, a steamship to Ceylon, ‘Tuition in Modern English Ballroom Dancing’.

Some have been graffitied. The model in a Brushwave poster (‘Today’s finest permanent wave’) has had thick-framed glasses and a moustache added with a black felt pen. Others have fared distinctly worse. It puts me in mind of Larkin’s ‘Sunny Prestatyn’, where the laughing girl in a tourism poster is subjected to this type of defacement: ‘A couple of weeks, and her face/Was snaggle-toothed and boss-eyed’. Before long, the vandals have set her astride ‘a tuberous cock and balls’. We are sometimes inclined to imagine that obscenity is an invention of our own times. ‘Sunny Prestatyn’, like the Brushwave poster, is from 1962.

The poem ends with the poster being pulled down and replaced: ‘a great transverse tear/Left only a hand and some blue.’ Down in the tunnel everything is torn – a half-hearted attempt, perhaps, to clean up when this section was closed off. Like the tunnel itself, the job was abandoned. What is left is a crust of papier-mâché dozens of layers thick. Through the tears in the paper we can look back in time, poster by poster, from the 1960s to the 1920s – from the Chatterley ban, if you like, to the age in which Lady Chatterley’s Lover was written and set. Back we go, through scraps of ripped, gummy paper, catching glimpses of the decades as we pass. Here is an advertisement for a new soap opera called Coronation Street and huge bold caps shrieking PSYCHO. Beneath these, adverts for Sterodyne ‘for coughs and colds’, the Theosophical Society, homes in Metroland.

A week later, at the annual conference of the Ephemera Society of America, an auctioneer is running us through his wish list of rare posters. Here is one advertising the Titanic. A rarity for sure. But look closely at the dates. It’s for the return voyage: New York to Southampton.