The only copy of a novel that has been signed twice by J.K. Rowling – once as herself and once under her male pseudonym, “Robert Galbraith” – is to go under the hammer at Sotheby’s London tomorrow, December 10. The first edition book is estimated at £2,000 - £3,000.

The Cuckoo’s Calling, published earlier this year, is an internationally bestselling crime novel about the murder of fictional supermodel Lula Landry. Rowling is most famous for penning the seven-part Harry Potter series – the best-selling book series in history, thanks to which she is the UK’s best-selling author since records began.

Rowling published the work under the pseudonym Robert Galbraith in April, when it sold just 1,500 copies. However after the author’s true identity was revealed in July, it shot up from 4,709th place on Amazon’s list of best-selling novels to first place. A sequel also written under the Galbraith pseudonym is slated for publication next year.

Proceeds from the auction will benefit EdUKaid, a British charity that works to improve teaching standards and learning environments in small Tanzanian villages. They aim to support children, families and schools by building classrooms and providing educational support for pupils and teachers.

The auction and fundraising event is the personal project of Margaret Darling, the wife of former Chancellor of the Exchequer Alasdair Darling. Rowling donated the work to Darling, said to be a friend of hers, in order to assist the fundraising efforts.

“Jo [Rowling] knows the value of education. She was a teacher. Her very special gift will allow EdUKaid and the community to put desks, water, sanitation, [and] blackboards into schools [in rural Tanzania],” Darling said. “The villagers and the children have little except hope. Our aspiration is for the Sotheby’s auction, which will be seen around the world, to help see some of these hopes realised.”

“English Literature, History, Children’s Books & Illustrations sale,” Sotheby’s London, Tuesday 10 December 2013