JK Rowling seems to have been keeping herself busy lately.

Not only does she have a new movie project in the pipeline, but she's found the time to write a short story about a character who was only referred to in the Harry Potter books.

Published on the Pottermore site, the new tale apparently takes the form of a biography of Celestina Warbeck - aka "The Singing Sorceress".

She explained to Today: "Celestina Warbeck is one of my favourite 'off-stage' characters in the Harry Potter series, and has been part of the Potter world ever since its inception, making an early appearance in the short-lived 'Daily Prophet' series I produced for members of the equally short-lived fan club run by my British publisher, Bloomsbury.

"Although we never lay eyes on Celestina during the whole seven volumes of the Potter books, I always imagined her to resemble Shirley Bassey in both looks and style.

"I stole her first name from a friend with whom I worked, years ago, at Amnesty International's Headquarters in London; 'Celestina' was simply begging to be scooped up and attached to a glamorous witch."