Playfair was educated at Cheltenham College and joined the Royal Engineers in 1913. He served in France and Belgium during World War I, during which he was mentioned in despatches, awarded the Military Cross (MC) and bar, and the Distinguished Service Order (DSO).
Playfair was appointed Officer Commanding Gentlemen Cadets, Royal Marine Artillery in 1920, a post he held until 1924.
In 1930, he married Jocelyn Malan, with whom he would father two sons.
Between 1930 and 1934, he was chief instructor in field works and bridging at the Royal School of Military Engineering. In 1934, Playfair became an instructor at the Indian Army Staff College, in Quetta. In 1938, he transferred to the Imperial Defence College, and in 1939 he was appointed Commandant of the Army Gas School, in Wiltshire.
In 1940, following the outbreak of World War II, Playfair was appointed Director of Plans at the War Office. In early 1942, he was appointed deputy commander (and chief of staff) of land forces in the American-British-Dutch-Australian Command (ABDACOM), a short-lived, supreme command for Allied forces in South East Asia and the south west Pacific. In 1943, Playfair was appointed to the general staff of the 11th Army Group, in the South East Asia Command.
Playfair retired in 1947. He later wrote several books, and was co-author of a World War II official campaign history, The Mediterranean and Middle East.