still a young man, as few documents relating to his early career have survived. However, his early promotion was not usual at that time; other men of Mitchell's age held similar positions in other aircraft companies. Decades after his death, when approached for information about him, those surviving Supermarine colleagues who had known Mitchell were reluctant to recall their personal memories. 1920s civilian and military aircraft designs Between 1920 and 1936, Mitchell designed 24 aeroplanes. His early projects often involved adapting Supermarine's earlier aircraft; in June 1920 the Air Ministry announced a civilian aircraft competition, and Supermarine's entry for the competition was the Commercial Amphibian, an adaptation by Mitchell of the company's Supermarine Channel. The Amphibian finished second, but was judged the best of the three entrants in terms of design and reliability. His redesigned Supermarine Baby, renamed the Supermarine Sea King, was exhibited the Olympia International Aero Exhibition in 1920, the first international exhibition to be held in the UK since the end of World War I. In 1922, the Chilean government bought a Channel, modified by Mitchell. That year he redesigned a version of the Commercial Amphibian, the Supermarine Sea Eagle. Mitchell produced new designs for aircraft early in his career; he designed the Supermarine Seal II in 1920, and the triplane Flying Boat Torpedo Carrier the following year. The historian Ralph Pegram notes that the unbuilt Torpedo Carrier reveals the "first true indication of Mitchell’s thoughts as a designer". In 1921 work began on the Supermarine Swan, a commercial carrier, but only the prototype was built. The Supermarine Seagull II—later used as the basis for future designs—began to receive production orders in 1922. The Amphibian Service Bomber was designed by Mitchell in 1924. Renamed the Supermarine Scarab, 12 aircraft were bought by the Spanish Navy; they remained in service until 1928. Supermarine's first design for a land aircraft, the Supermarine Sparrow, competed unsuccessfully during the Air Ministry's Light Air Competition of 1924, and subsequently failed to gain orders. A variant, the Supermarine Sparrow II, was used by Mitchell to test his different airfoil designs. Work on the Supermarine Southampton started in March 1924. It flew for the first time the following March, and entered service in July 1925. By the end of 1925, Mitchell's team had designed the Southampton II—the Southampton but with a metal hull. The plane, more powerful, lighter, and more durable than its predecessor,