A CODEBREAKER who decrypted Nazi war secrets has been enshrined on a wall in Oxford.

Joan Murray has been honoured with a blue plaque, which was unveiled on Saturday outside her former house in Larkfields, Headington Quarry.

Dozens of people gathered at the ceremony, learning about her vital role at Bletchley Park and later at GCHQ.

Mrs Murray was also known for her relationship with Alan Turing, to whom she was engaged, and she was portrayed in the film The Imitation Game by A-list actress Keira Knightley.

Robert Evans, chairman of Oxfordshire Blue Plaques Board, said at the ceremony: “A lot of what happened [at Bletchley] will remain secret, and that’s part of the fascination about its history.

“I wonder whether she chose this residence precisely because it was rather private and quiet, and she wasn’t keen on making any sort of public impression in terms of her career.”

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Mrs Murray, née Clarke, moved to number 7 in the latter years of her life, and died in the house in September 1996, aged 79.

Kerry Howard, a researcher specialising in history of women in the Second World War, said she was ‘privileged’ to be among special guests at the ceremony.

She gave a detailed speech about Mrs Murray's life and work, before unveiling the plaque to rapturous applause.

A member of the public had approached the Oxfordshire board suggesting Mrs Clarke was worthy of a plaque.

The current homeowners, Sam and Steve Demant, gave permission for it to be placed on the wall and even saved the board a bit of money by offering to mount it themselves.

Mrs Demant said shortly after they moved in seven or eight years ago, a neighbour made them aware of their property’s former inhabitant.

She added: “When [the board] approached us, we were happy to help.

“There are far fewer blue plaques commemorating women [compared to men], so it’s rather nice to host a blue plaque for a prestigious woman.”

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Councillors Roz Smith, Chewe Munkonge, Timothy Hallchurch, deputy Lord Mayor of Oxford Mohammed Altaf Khan and Oxfordshire County Council chairman Les Sibley attended.

Ms Smith said: “I have learned so much today about what an amazing woman Joan was.

“It’s wonderful to have that little bit of history here in Headington.”

Mr Munkonge added: “It’s important to appreciate the work of the women [in the Second World War.]

“It’s good to be celebrating her life with the unveiling of this plaque.”

Mrs Murray's nephew John Clarke, who travelled from Maidenhead to attend the ceremony, added: “It’s nice that people will know she was here.”

There are now more than 100 blue plaques in Oxfordshire, each honouring a special person or event, and about half are concentrated in Oxford.

There are seven others in Headington, including for Edward Brooks VC and well-known Morris dancer William Kimber.

Each blue disc costs about £500 to create and mount.