A 92-year-old woman has been buried in the US with British military honours for a secret that she held for decades – her Second World War service as part of the Enigma codebreaking team.

The Union flag was draped over Jean Briggs Watters’ coffin during her funeral on Monday, the Omaha World-Herald reported.

She had died on September 15.

The tribute honoured Mrs Watters for her role decoding for the top-secret military programme led by Alan Turing, who was the subject of the 2014 Oscar-winning film The Imitation Game.

Jean Watters funeral
Robin Watters reads from the programme during the funeral of his mother Jean Watters at the Omaha National Cemetery in Omaha, Nebraska (Chris Machian/Omaha World-Herald via AP)

Mrs Watters was among about 10,000 people, mostly women, who took part in the Allied effort to crack German communication codes throughout the war.

She operated an electro-mechanical machine known as a bombe, to decipher signals the German armed forces sent out from its Enigma encryption machines.

The programme at Bletchley Park saved lives and helped bring an end to the war. But it was kept classified until the 1970s.

“She never told anyone,” said Mrs Watters’ son, Robin.

“She was fully aware of the gravity of what she was doing. It was haunting to her, what might happen if she made a mistake.”

Jean Briggs Watters was 18 when she enlisted in the Women’s Royal Naval Service.

She had attended an art school in Cambridge before joining the war effort.

She met her husband, a US Army Air Corps pilot named John Watters, during the war and they married soon after.

She and her husband retired to the US in 1969.

Mrs Watters was buried Monday in a plot next to her husband, who died in June at the age of 101.

“She had a seriousness, and a sense of duty,” Robin Watters said.

“She was a really special lady. But she was tough. She did the hard things.”