Born in Buckinghamshire, Derek George Montague Gardner’s father worked in the Docks at Grimsby and became Chief Engineer of the Port of Glasgow in 1928, it was from this that he developed a love of ships.
Educated at Oundle School, where he won a prize for his drawing. He trained as a civil engineer in Glasgow with the London Midland and Scottish Railway upon leaving school in 1931, and later he joined Sir William Arrol & Co. Gardner joined the RNVR as a 20 year-old midshipman and took up painting watercolours of warships.
In 1939, shortly after the Second World War broke out, Gardner served as an anti-submarine officer on the Royal Navy Destroyer HMS Broke. Later in 1943 he joined the Destroyer HMS Highlander. After the war he joined the Colonial Service, serving in Kenya from 1951. Gardner lived in Kisumu by Lake Victoria before moving to Nakuru where he painted oils, watercolours and pastels of local scenes such as flamingos on a nearby soda lake.
Gardner returned to England with his Family in 1963 retiring to Dorset. He turned to painting maritime subjects and his detailed paintings found a ready market. He held several exhibitions in London, was a Fellow of the Institution of Civil Engineers and a member of the Royal Society of Marine Artists. He was best known for his paintings warships from the Napoleonic Wars and paintings of clippers from later in the 19th Century.