The earliest draft version of Withnail and I is to go under the hammer at Sotheby's on December 15.
Bruce Robinson's short novel, which he described as "70% autobiographical", was written in 1969-70.
Its author was living in a house in Camden Town, north London, in which much of the debauched action takes place.
The draft offered for sale includes extensive revisions in Robinson's hand, along with a single leaf torn from a magazine which features a photograph of the author and his flatmates outside their house in the late 1960s.
The iconic 1987 film, which starred Paul McGann and Richard E Grant, had a protracted journey to the big screen.
In the 1980s, a copy of the unpublished novel reached executive producer Mody Schreiber.
He commissioned Robinson to adapt it for the screen and the Beatles' George Harrison read the script on a transatlantic crossing.
Harrison's company Handmade Films, formed to fund Monty Python's Life of Brian, ended up producing the comedy, which was directed by its writer.
Withnail and I has become a much-loved and oft-quoted favourite.
Set at the end of the 1960s, it tells the tale of two out-of-work actors, Withnail (Grant) and 'I' (McGann), who exist on a diet of booze, drugs and cigarettes in their revolting Camden flat.
Robinson's housemates - including Vivian MacKerrell, who was famously the basis for Withnail, and David Dundas, who wrote the film's music - were still drama students at the nearby Central School of Speech and Drama at the time they were living together.
The draft for Withnail and I is estimated at between £4,000-6,000 and is offered as part of Sotheby's sale of English Literature, History, Children's Books and Illustrations.