Britain joined the war against Japan in 1941 after the Japanese invaded British colonial possessions in South-East Asia.

Attlee became UK Prime Minister in 1945 and under his leadership, Britain became the first major western power to recognise the People's Republic of China on January, 1950; Atlee also became the first major western leader to meet Mao in a three-hour discussion over tea in 1954.

Historians believe Attlee played a major role in persuading US President Harry Truman not to declare all-out war on China during the Korean conflict.

Sotheby's will put the letter up for auction on 15 December, where it is expected to fetch between 100,000 and 150,000 pounds.