In 1912, he passed the examination for what was then called second division clerkships and was appointed to the Foreign Office. He served as a member of the East Registry. A keen volunteer when World War I broke out, he was allowed by the Foreign Office to join his field artillery unit, being promoted second lieutenant in 1917 and serving in that capacity in Palestine. As a humble clerk, he had performed only routine duties but distinguished himself through his assiduity and retentive memory. Thus, when the war ended he was selected under the special recruitment scheme for filling vacancies caused by the war and appointed to the Levant Consular Service. After a short period of training in Oriental languages at King's College, Cambridge, he went as Vice-Consul to Thessaloniki, and soon after became third Dragoman at Constantinople. When the Turkish capital moved to Ankara and the office of Dragoman was abolished, Helm went there as Second Secretary. He served there as Consul, and in 1930 was transferred to the Foreign Office, working in the Eastern Department. In 1937 he was sent as Consul to Addis Ababa and at the outbreak of World War II was moved to the British Embassy at Washington, D.C., where he handled the various complicated problems connected with the supply of petroleum to the United Kingdom. In 1942 he went back to Ankara as Counsellor. , Sir Knox Helm, Leslie Hore-Belisha and Moshe Sharett in the Israeli Knesset, 1951 In 1946 he was chosen to go as British representative to Hungary and when normal diplomatic relations were restored in 1947 he was made Minister there. In 1949 he was appointed the first British Chargé d'Affaires to Tel Aviv in the newly independent State of Israel, where he spent two happy and fruitful years; in 1951 he became Ambassador to Turkey. He left there in 1954, having reached retirement age, but went for a brief period to Khartoum in 1955, being the last Governor-General there. "Helm was a man of strong character and great determination. A tenacious and forceful negotiator, he had great powers of persuasion and a remarkable sense of timing – valuable gifts which were supplemented with a sense of humor and of proportion and charm which was genuine: few people can ever have said 'No' in a more pleasant way. He was an exacting chief but popular with his staff, who always knew that he could do any of their jobs better than they could themselves. Moreover, he was always ready to listen to their advice, but equally, he invariably made up his own mind." "He retained to the end the accent and intonation of the Dumfriesshire farming stock from which he came and his love for and understanding of the things of the soil often stood him in good stead in posts where agricultural problems bulked large in the economy of the country." — The Times
