Call for new museum to honour the secret listeners who spied on the Nazis

More than 2,700 people have signed the petition to convince developers Berkeley Homes, who bought the grounds in September, to establish a museum in the mansion.

Requisitioned from Sir Philip Sassoon by the War Office soon after the war started, the now-listed building is "a site of national significance," according to Ms Fry, who wrote The M Room: Secret Listeners who Bugged the Nazis in WW2.

"It's an important story, and if we're not careful it could be lost forever. And that would be tragic.

"The most crucial piece of evidence was about Hitler's secret weapon," she said. "In March 1943, it was discovered at Trent Park that he had a secret site in north Germany where they were developing the V1 and V2 rockets.

"The generals thought they were on their own, completely unguarded and relaxed, so they spoke about their concerns that they were losing the war, and one of the generals said 'Don't worry, we've got the secret weapon.'"

The historian said that the work of German-Jewish refugees, who listened as Nazi generals described the horrors of concentration camps, made vital discoveries like this possible.

"Not only were they hearing military information, they were hearing details of the atrocities, and many of them had relatives back in Germany and so would immediately worry about the fate of those they left behind," she said.