Born in St Albans, Hertfordshire, Swinson attended St Albans School. He enlisted in the Rifle Brigade in 1939 and in 1940 was commissioned into the Worcestershire Regiment. With the Worcestershire Regiment he fought at Kohima. The diaries he kept during the battle are now lodged in the Imperial War Museum. He served until 1946, with postings in Malaya, Burma, Assam and India during World War II. He served at Kohima, India. He subsequently became a writer and producer at the BBC where he produced a number of programmes for Richard Attenborough.