Miles Dempsey, the son of a marine insurance broker, was born in New Brighton, Wallasey, Cheshire, on 15th December, 1896. He was educated at Shrewsbury School. After graduating from Sandhurst Military Academy in 1915 he joined the Royal Berkshire Regiment.
During the First World War he served on the Western Front in France and as well as being mentioned in dispatches was awarded the Military Cross for bravery. On 12th March, 1918, he was gassed at La Vacquerie. This resulted in him later having a lung removed.
Dempsey remained in the British Army and by 1939 had reached the rank of lieutenant colonel. On the outbreak of the Second World War Dempsey was sent to France as commander of the 13th Infantry Brigade and during the Dunkirk evacuation he won the Distinguished Service Order.
In December 1942 Dempsey was promoted to lieutenant general and replaced Brian Horrocks as head of the 13th Corps in the 8th Army under the command General Bernard Montgomery. Dempsey was involved in the planning of the invasion of Sicily and led the assault on 10th July 1943. He advanced to the Straight of Messina on 3rd September 1943 and began to move through Italy.
In January 1944 Dempsey was given command of the 2nd British Army and took part in the D-Day landings on 6th June 1944. After coming under considerable pressure from General Erwin Rommel he finally broke out of the Normandy beachhead at the end of July. Dempsey's troops entered Belgium and liberated Brussels (3rd September) and Antwerp (4th September) before moving on to Holland. He crossed the Rhine on 23rd March, 1945 and captured Hamburg on 3rd May.
He succeeded General William Slim in Singapore and Malaya in 1945. The following year he was appointed as Commander in Chief of the Middle East (1946-47). After retiring from the British Army in July 1947 he published Operations of the 2nd Army in Europe.
In 1948, he married Viola O'Reilly, the daughter of Captain Percy O'Reilly, of County Westmeath, who represented Ireland in the Summer Olympics. Dempsey and "Tuppeny" as she was always known, shared a love of horses, and they purchased the Old Vicarage at Greenham. According to his biographer, Peter Roston, "the marriage, although not blessed with children, was extremely happy."
Dempsey was chairman of the Racecourse Betting Control Board. The RBCB had two functions: to present an alternative to bookmakers for betting; and to apply a proportion of its income from its betting activities for the good of racing. He was also chairman of Simonds Brewery (1953-1963) and deputy chairman of Courage, Barclay & Simonds (1961-1966).