Smiley attended the Royal Military College, Sandhurst, in 1934, and was commissioned into the Royal Horse Guards in 1936. While based in Windsor, Berkshire, with the Blues, he was seen as a "man-about-town", owning a Bentley car and a Miles Whitney Straight aircraft. He was also an amateur jockey and won seven races under National Hunt rules. After the outbreak of the Second World War in 1939, Smiley's regiment sailed for Palestine, where one of his first jobs was to shoot his troop of forty horses when it became clear they were of no use in modern combat. In 1940 Smiley joined the Somaliland Camel Corps, but was to arrive at Berbera the same day it was decided to evacuate British Somaliland. He returned frustrated to Egypt where he persuaded family friend General Wavell to recommend him for the newly formed commandos. Smiley was appointed a company commander with 52 Commando and his first mission was sneaking from Sudan into Abyssinia. He fought against Vichy French forces in Syria. For his reconnaissance work in ruins near Palmyra he was mentioned in despatches. Smiley was recruited by the Special Operations Executive 1943 and undertook his first operation with them in Palestine in the same year. Later 1943 he parachuted into Albania where he co-ordinated partisan operations for eight months, and was awarded an immediate Military Cross. In April 1944 Smiley and Lieutenant Colonel Neil " Billy" McLean again parachuted into Albania, carrying out guerrilla operations, for which Smiley was awarded a Bar to the Military Cross in 1944. He was invested as an Officer, Order of the British Empire in 1946. He was Colonel of the Royal Horse Guards between December 1951 to December 1954. He rode behind The Queen in the Gold State Coach in the Coronation Procession on 2 June 1953. He was invested as a Lieutenant, Royal Victorian Order in 1952 and received the Coronation Medal. He was British Military Attaché to Stockholm between 1955 and 1958. After the war, he held the record for the most falls in one season on the Cresta Run in St Moritz; bizarrely, he represented Kenya in the Commonwealth Winter Games of 1960. He was Commander of the Sultan of Muscat and Oman's Armed Forces between 1958 and 1961. He was Military Advisor to Yemen between 1962 and 1967.
Later work
Smiley was the author of three books based on his experiences, Arabian Assignment, Albanian Assignment and Irregular Regular. Smiley died on 9 January 2009, survived by his wife, Moyra two sons, Xan de Crespigny Smiley and Philip David Smiley, a stepson and a stepdaughter.