Keira Knightley too beautiful to play codebreaker Joan Clarke says former colleague: 'She looked like the back end of a bus'

Lady Jean Fforde went on to say that Clarke was a 'blessed woman'

Benedict Cumberbath as Alan Turing in The Imitation Game (Snap Stills/REX)

Keira Knightley was too beautiful to play mathematician Joan Clarke in the Oscar-winning film The Imitation Game, according to a former colleague - who said Clarke looked like the “back end of the bus”.

Lady Jean Fforde worked alongside Clarke and Alan Turing as they attempted to crack the German enigma code during the Second World War at Bletchley Park.

Author Tessa Dunlop, who interviewed Fforde at her home on the Isle of Arran, made the aside as she discussed her new book The Bletchley Girls: War, Secrecy, Love and Loss at Hay Literature Festival.

“She was nothing like Keira,” Fforde reportedly said of Clarke. “An absolute back end of a bus. Blessed woman, though.”

Clarke, played by actress Keira Knightley alongside Benedict Cumberbatch’s Alan Turing, was among the few women in the now-famous Hut 8.

It is not the first criticism has been levelled at the casting of Knightley, who reportedly gave birth to her first child with husband James Righton today, as Clarke.

Shortly after the film wrapped, Turing’s niece Inagh Payne described her uncle’s one-time fiancé as “rather plain” in an interview with the Mail on Sunday.