Gwynne Jones was born in "modest circumstances" in Monmouthshire. He was educated at West Monmouth School, and subsequently at the School of Slavonic Studies at the University of London. Joining the South Wales Borderers when the Second World War broke out, he was commissioned a second lieutenant on 2 November 1940. From 1941 to 1944 he fought in Burma alongside the Welsh poet Alun Lewis. On 1 January 1943, he received an emergency commission in the Royal Armoured Corps as a war-substantive lieutenant, with the same rank in the South Wales Borderers from 1 April. After the war, Gwynne Jones remained in the Army, receiving a substantive lieutenant's commission in the South Wales Borderers on 24 August 1946 (with seniority from 5 June 1942), and was promoted to captain on 5 December. He was awarded the Efficiency Medal in October 1950. Promoted to major on 5 December 1953, Gwynne Jones took part in a series of anti-terrorist campaigns, and was decorated with the Military Cross (MC) in August 1957 for commanding a company which fought in the Malaysian jungles during the Malayan Emergency, after his involvement in a series of ambushes against communist insurgents. Gwynne Jones later stated, "I was lucky enough to carry out some successful ones." The citation reads as follows:  Gwynne Jones was brevetted to lieutenant-colonel on 1 July 1960, and was decorated as an Officer of the Order of the British Empire (OBE) in the 1961 Birthday Honours. He retired from the army on 30 June 1961 with the honorary rank of lieutenant-colonel. Entering politics, he was a minister in the Foreign and Commonwealth Office from 1964 to 1970 and from 1964 was appointed to the Privy Council. He was created Baron Chalfont, of Llantarnam in the County of Monmouthshire on 11 November 1964. Following the death of Lord Shawcross in 2003, his life peerage was the most senior extant, and Lord Chalfont was placed higher in the order of precedence than four hereditary barons whose inherited titles were created after his. On 27 March 1967, in the House of Lords, Chalfont became the spokesman/figurehead for Harold Wilson's Labour Party Government's attempt to divest Britain of the Falkland Islands. In November 1968 Chalfont travelled to the Falklands to canvas the people, and try to persuade them of the merit of becoming Argentine citizens. He was sent away in no doubt that the islanders wished to remain British, but, on his return to Britain, he reported, "I do not believe that the Falkland Islands can continue to exist for many years, as they are presently constituted.