[1] Freeman Dyson, a fellow pupil at Winchester, has described Thompson's extraordinary facility with diverse languages and that "Frank was the largest, the loudest, the most uninhibited and the most brilliant."

[3] In 1939, while studying at the University of Oxford, he became a member of the Communist Party of Great Britain under the influence of his close friend Iris Murdoch.

Despite his affiliation, he did not support the party's policy of neutrality dictated by the Molotov–Ribbentrop Pact and joined the British Army with service number 124039 as a volunteer training with the No.

The commandos carried a radio to keep in contact with the staff in Cairo, Egypt and Bari, Italy, but it broke down.

On 23 May, Thompson took part in the clash at the village of Batulia between the Bulgarian Gendarmerie and the Second Sofia Brigade of National Liberation of the partisans.