Campaigners are fighting to preseve the site where intelligence about the Holocaust was gathered by German Jewish refugees from high-ranking Nazis.
Trent Park mansion, in north London, was used as a prisoner of war camp during the Second World War, for 59 senior German generals, including Hitler's deputy Rudolf Hess.
Their conversations about the genocide of the Jews, the Nazi atomic bomb programme and U-boat tactics were secretly monitored by Jewish refugees, recruited by MI6 because they were fluent in German.
Helen Fry, the historian leading the campaign, said that without the intelligence gathered at Trent Park, "I don't think we would have won the war."
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.