Tufton Beamish was born at Pitliver, Dunfermline in Fife on 27th January 1917. His father, Tufton Percy Hamilton Beamish, was a rear-admiral in the Royal Navy and would later become Conservative MP for Lewes. Beamish Jr. was highly influenced by his upbringing in a military and political household. He was educated at the Royal Military College, Sandhurst, which further influenced his development.
In 1937 Tufton Beamish was commissioned into the Royal Northumberland Fusiliers as a 2nd lieutenant. In 1937 and 1938 he served in the British military mission in Cairo. In 1938 and 1939 he served in Palestine. After the outbreak of the Second World War, he was sent to France with the British Expeditionary Force, with whom he served as a company commander. The following year, on the retreat to Dunkirk, he was wounded. In 1941, after recovering from his injuries Beamish was sent to Singapore with the 18th Division. He avoided capture at the fall of Singapore by escaping to Ceylon in a rowing boat with seven other men.
Beamish left the Army in 1945 with the rank of Captain.