He is best remembered as the diplomat whose secrets were stolen by his Kosovar Albanian valet and passed on to Nazi Germany.

[10] In the summer of 1937, while travelling between Nanking and Shanghai in an embassy car, Knatchbull-Hugessen and his companions were machine-gunned by a Japanese fighter aircraft; he was the only one hit.

[13] In 1943, Knatchbull-Hugessen oversaw secret talks with diplomats from the Hungarian Embassy who wanted to sign an armistice with Britain.

On 9 September 1943, aboard a yacht in the Sea of Marmara, Knatchbull-Hugessen concluded a preliminary armistice agreement with László Veress, an official of the Hungarian Ministry of Foreign Affairs.

[15] From November 1943 to March 1944, his Kosovar Albanian chauffeur and valet, Elyesa Bazna, known under the cover name Cicero, regularly opened his mail and safe, selling any useful information to German High Command; one of the more damaging spying incidents of World War II.

[18] On 16 July 1912, he married Mary Gordon-Gilmour (1890–1978), daughter of Brigadier-General Sir Robert Gilmour, 1st Baronet.