By Caroline Briggs
Entertainment reporter, BBC News
An unpublished novel by renowned author Jeanette Winterson has been found at an Underground station in south London.
Martha Oster said she is a fan of Winterson's work
The Stone Gods, by the writer of Oranges Are Not The Only Fruit, is not due to be published until September.
Martha Oster, 27, said she was "amazed" when she found the 134-page manuscript lying on a bench at Balham station on Wednesday night.
Simon Prosser, of Penguin, said it was accidentally left by someone who works for the publishing house.
Mr Prosser, the company's publishing director, said the incident was "terribly unfortunate," but added it was simply human error.
"If someone is reading a manuscript on the Tube home or the bus as they often do, then it is very possible that you might leave it," he said.
"In this case someone was reading the manuscript, or partial copy of the manuscript, and because it was late, left it behind.
"She went back to the station to try and retrieve it, spoke to the cleaners, but could not find it anywhere."
Ms Oster, a teacher from Tooting, south London, was returning from a night out with colleagues when she spotted the manuscript.
Winterson won the 1985 Whitbread Prize for a first novel for Oranges
She said: "I sat down to wait for my train and it was just lying on the bench. There was no-one around, so it had obviously been left by someone.
"I'm nosey so I picked it up, had a flick through, and realised what it was.
"I was amazed to find it like that."
Ms Oster said she recognised Ms Winterson's name immediately.
"I studied Oranges Are Not The Only Fruit for A-level, and I have a couple of her books at home."
"She is one of my favourite authors, so I recognised her name straight away, and the writing is very much in her style."
Caroline Michel, Winterson's agent and managing director of the William Morris agency, said Winterson was out of the country and was not aware of what had happened.
She said the incident was "highly regrettable" but had been assured by Penguin that it would not happen again.
"I have spoken to Penguin about it and we are aware of how it happened. It was an accident," she said.
"It is not something that happens every day, thank goodness."
Winterson, 45, wrote the controversial Oranges Are Not The Only Fruit, about a lesbian girl who grows up in a religious community, when she was just 23. It was later dramatised for the BBC.
Her other novels include The Passion, Sexing The Cherry, Written On The Body, The Powerbook and Lighthousekeeping.
Her books for children include The King of Capri and Tanglewreck.
In 2006 Winterson was appointed OBE for services to literature.