of Bengal. Macmillan would subsequently write of the attempt in his 1937 book, Freelance Pilot. The flying journal Aeroplane appeared to have little respect for the expedition, printing a weekly satirical cartoon based on the then popular Adventures of Pip, Squeak and Wilfred serial, as "The Adventures of Mac, Broome and Wilfred", followed by a satirical letter addressed to "My Dear Pilots and Ground Wallahs". During the early 1920s, Macmillan worked as a free-lance test pilot, unattached to any particular company. He flew Fairey aircraft from 1921, and also took five Parnall aircraft on their first flights, taking part in the 1923 Lympne light aircraft trials, demonstrating the Parnall Pixie aircraft. Macmillan eventually joined Fairey full-time in early 1925 as chief test pilot and stayed with them until the end of 1930. He then became chief consultant test pilot to Armstrong Whitworth Aircraft. In 1925 he was the first to land (an emergency landing) at Heathrow, which then was a row of cottages in land used for market gardening. In addition to flying Macmillan wrote numerous magazine articles, as well as books on aviation, including a series detailing the history of the Royal Air Force during the Second World War. Despite being partly written during the war they are remarkably detailed and accurate. He served in the Royal Air Force during World War II as a war correspondent, rising to the rank of acting wing commander. On 12 April 1946 Macmillan was commissioned as a pilot officer in the Royal Air Force Volunteer Reserve (Training Branch), and was promoted to flying officer on 1 April 1947. On 12 April 1954 his period of service was extended for another four years. Macmillan also served as the commander of the Cornwall Wing of the Air Training Corps from 1945 until 1958, and was the First RAF member of the Cornwall Territorial and Auxiliary Forces Association from 1947 to 1961, twice serving as Vice-Chairman (Air). He was also the President of the National League of Airmen, a founder associate member of the Institution of Aeronautical Engineers in 1919, and was made an Associate Fellow of the Royal Aeronautical Society in 1928, and in 1929 was one of the founders of the Guild of Air Pilots and Air Navigators, a first Warden, Deputy Master (1934–35), and a Freeman and Liveryman of the Guild. Among his other achievements Macmillan was the first pilot to fly