HE is credited with saving countless lives and shortening the Second World War by two years.

He was voted the 21st Greatest Briton of all time in a popular BBC series.

And yet when Rachel Barnes of Blagdon Hill, near Taunton, tells people that her great-uncle was Alan Turing, the great mathematician and codebreaker who helped crack the Nazi’s Enigma machine, she is often met with blank stares.

All that is likely to change when a major feature film about Turing – starring Benedict Cumberbatch and Keira Knightley – hits the big screen on Friday.

The Imitation Game tells the story of Turing’s time at Bletchley Park, which was the heart of the Government’s Code and Cypher School during the war.

It also details his tragic personal life – after the war Turing was prosecuted for being gay and was chemically castrated.

This caused him to suffer depression and in 1954 he committed suicide at the age of 41.

Rachel, a technical support officer with Somerset County Council, was born in 1963, nearly a decade after her great-uncle died, but she says: “Growing up he was always talked about in my family – not just the fact that he was brilliant but also the way he was treated by the Government in his last years.

“When I start thinking about what happened, and what might have been, it’s really quite upsetting.

“My mum (Inagh Paine, Turing’s eldest niece) was 18 when he died. She says that he was extremely kind and caring and very, very generous.

“He was just an ordinary man and a very caring uncle – now the whole of his story seems to be coming out into the world.

“It’s wonderful for the family that Alan’s legacy is going to be known.”

When she discovered that a film about Turing was in the pipeline, Rachel emailed the company behind it, Black Bear Pictures, to find out more, although she says she wasn’t expecting a reply.

However, within 24 hours the producer, Teddy Schwarzman, replied to thank Rachel for her interest and to say that he would be very keen to find out more about the Turing family.

Fast-forward two years and Rachel is now getting ready to see the finished film with friends at The Odeon in Taunton this weekend.

It won’t be her first viewing, however.

Rachel and her family were treated to a private screening in September, and last month attended the film’s premiere in Leicester Square, London, before heading to a gala party at The Roundhouse, where they met Benedict Cumberbatch, who plays Turing in the film.

Rachel said Cumberbatch was “absolutely charming” and the past few months had been “a mind-blowing and brilliant experience”.

As for the film itself, Rachel said: “Everybody thought it was incredible – absolutely brilliant.

“We are so grateful to Black Bear Pictures and Studio Canal for making this film about Alan so that his legacy will now be known by a wide audience.

“We were really hoping that the filmmakers would treat our uncle with the utmost respect and they have.

“Benedict has done the most amazing job. He spent months researching the role and the character he has produced is so like Alan.”

Turing’s legacy continues to live on through Rachel’s family.

She is married to Mark and has three children, Tom, aged 20, and twins Anna and George, both aged 17, who attend Richard Huish College in Taunton.

Rachel said: “As a family we have been totally inspired by Alan, particularly my eldest, Tom.

“He has been interested in IT since he was tiny and is now in the final year of a degree in forensic computing.

“As a family we’ve been invited to so many events because of our connection to Alan, and last week Tom was invited to Google’s head office in London, where he ended up sitting next to the ex-head of MI5!”

Rachel hopes The Imitation Game will help give her great-uncle the recognition he deserves.

She added: “Over the years most people I speak to have never heard of him.

“Possibly the next time I mention that I’m the great niece of Alan Turing I won’t get so many blank stares – especially if I mention Benedict Cumberbatch!”