A grandmother who was sworn to secrecy for her work decoding enemy messages during World War II has just received a war medal.

Accountant Gwen Churcher, from Caldbeck Avenue, Worcester Park, was only 17 years old when she was selected to go to Bletchley Park, Buckinghamshire, to work alongside the country’s top academics breaking top secret codes on the German military’s Enigma machine.

For more than 30 years Mrs Churcher was not allowed to reveal what she did to friends, family or even her husband.

This week the 86-year-old received a service medal signed by Gordon Brown. Last year the Government decided to recognise the efforts of the 10,000 people who worked at Bletchley Park.

Mrs Churcher worked at Bletchley from 1942 to 1945.

She said: “We dealt with all kinds of codes – and everyone who worked there was sworn to secrecy.

“We were told to tell our family and friends anything, but not what we did. My husband didn’t even know.

“We worked on the codes 24 hours a day – you either worked 9am to 4pm, 4pm to midnight or midnight to 9am.”

Many historians believe the work at Bletchley tipped the balance of the war.

Mrs Churcher said: “I found out the Government had started giving out medals and decided not to apply for one. But my family nagged me to get one so I filled in a form and the medal arrived in the post this week.”

Even today, a lot of information about the work carried out at Bletchley is classified.