Churchill tried to block Duke of Windsor '˜Nazi' papers, secret files reveal

Captured German telegrams showed that its foreign minister, Joachim von Ribbentrop, believed the Duke to be “sympathetic” and had hoped to lure him to neutral Spain in order to offer him the throne as part of an elaborate plan to persuade Britain to make peace.

One German agent reported the Duke “did not fear the King (his brother, George VI), who is altogether stupid, as much as the clever Queen.”

After the war, historians wanted to publish the exchanges. But the National Archives files show Churchill tried to delay their release for up to 20 years amid concerns they would cast doubt on the loyalties of the Duke, who had abdicated the throne in 1936 to marry the American divorcee, Wallis Simpson.

In 1953, he even wrote to US President Dwight Eisenhower, appealing to his sense of “justice and chivalry”.

“If they were to be included in an official publication they might leave the impression that the Duke was in close touch with German agents and was listening to suggestions that were disloyal,” Churchill wrote.

Despite his misgivings, the telegrams were finally published in 1957 after the historians in charge of the release programme threatened to resign.