'There's been this huge mystery'

The first chapter of Harper Lee's Go Set a Watchman - a previously unpublished successor to 1960's Pulitzer Prize-winning To Kill A Mockingbird - has been published online by the Guardian ahead of the book's publication next week.

The book was completed in the 1950s prior to Mockingbird's creation and the original manuscript was considered lost until Autumn 2014, when it was discovered by Lee's lawyer.

"There's been this huge mystery as to what it was that pre-existed To Kill a Mocking Bird," said Claire Armitstead, head of books at the Guardian.

In scholastic circles it has been known that the piece existed, she said.

"But to the wider public it seemed about as likely as the Pope giving birth that Harper Lee would come up with this novel at the age of 88, when it was discovered."

Read the first chapter of Harper Lee's new novel.