|Representing Great Britain|
|1968 Mexico City||Team eventing|
|1968 Mexico City||Individual eventing|
|1957 Copenhagen||Team eventing|
|1967 Punchestown||Team eventing|
|1969 Haras-du-Pin||Team eventing|
|1959 Harewood||Team eventing|
|1959 Harewood||Individual eventing|
|1965 Moscow||Team eventing|
|1967 Punchestown||Individual eventing|
Major Derek Swithin Allhusen, CVO (9 January 1914 – 24 April 2000) was an English equestrian who was a 54-year-old grandfather when he rode Lochinvar to team gold and individual silver medals at the 1968 Summer Olympics in Mexico.
Derek Swithin Allhusen was born in London and educated at Eton and Trinity College, Cambridge. In 1937 he married The Hon Claudia Betterton. He served throughout the Second World War with 9th Queen's Royal Lancers, being awarded the American Silver Star in 1944.
On returning from Germany he brought back two horses with him and settled in Claxton, Norfolk. He rode one of the horses, Laura when representing Britain in the pentathlon at the 1948 Winter Olympic Games. He eventually took up eventing in 1955, riding Laura's daughter Laurien on two European Championship teams, winning a team gold medal in 1957, then team silver and individual bronze in 1959. In 1961 he bought Irish-bred Lochinvar and rode her in two winning European Championship teams (in 1967 and 1969) as well as the gold and silver at the 1968 Summer Olympics. He was awarded an MBE for his achievements but declined it; feeling his team-mates Richard Meade, Jane Bullen and Reuben Jones also deserved recognition.
On his retirement from the sport he continued as a breeder and Laurien's son Laurieston was ridden to team and individual Olympic gold medals in 1972 Games in Munich, with Richard Meade in the saddle. Allhusen was president of the British Horse Society from 1986 to 1988.
Allhusen was appointed to be one of Her Majesty's Body Guard of the Honourable Corps of Gentlemen at Arms in 1963, he was appointed Standard Bearer from 1981 to 1984. He was appointed to be a Commander of the Royal Victorian Order in 1983.
- "Allhusen, Derek S.". U.S. Army Awards of the Silver Star for Conspicuous Gallantry in Action During WORLD WAR II. HomeofHeroes.com. Archived from the original on 7 June 2008. Retrieved 2007-12-13.
- The London Gazette: . 30 May 1946. Retrieved 2008-12-28.
- The London Gazette: . 26 November 1963. Retrieved 2008-12-28.
- The London Gazette: . 27 January 1981. Retrieved 2008-12-28.
- The London Gazette: . 10 January 1984. Retrieved 2008-12-28.
- The London Gazette: . 31 December 1983. Retrieved 2008-12-28.
- The London Gazette: . 15 November 1955. Retrieved 2008-12-28.
- The London Gazette: . 13 November 1956. Retrieved 2008-12-28.
- The London Gazette: . 18 March 1958. Retrieved 2008-02-06.
- "Derek Swithin Allhusen CVO DL". British Olympic Association. Retrieved 2007-12-13.