An unpublished novel by renowned author Jeanette Winterson was found at Balham Underground station.
A 134-page manuscript of The Stone Gods, not due to be published until September, was picked up from a bench on Wednesday night.
Martha Oster, 27, a teacher from Tooting, was returning from a night out with colleagues when she spotted the manuscript.
She told BBC News: "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.
"She is one of my favourite authors, so I recognised her name straight away, and the writing is very much in her style."
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 23.
Other novels include The Passion, Sexing the Cherry, Written on the Body, The Powerbook and Lighthousekeeping.
In 2006 Winterson was appointed OBE for services to literature.
Penguin's publishing director said her latest manuscript was accidentally left at the station by someone who works for the publishing house.
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