It is a harrowing tale of torture in a colonial prison in Kenya that is said to explain the President’s coolness towards Britain and even his removal of Winston Churchill’s bust from the Oval Office.

David Maraniss, the author of Mr Obama’s most comprehensive biography so far, said five associates of Hussein Onyango Obama doubt he was even jailed. One told him: “People make up stories”.

Mr Onyango, a Muslim convert who worked for the British Army in Burma during the Second World War, was accused of sympathising with the burgeoning pro-independence movement that eventually turned into the Mau Mau rebellion in 1952. . .