Myles was the only child of Bertram Edward Joseph Petre and his wife Ruth Seymour. He was born in Thakeham, Sussex.
He was educated at Ampleforth and Matriculated in 1931. He graduated in 1934 and having been a Cadet CSM in the Ampleforth Contingent of the Junior Division OTC, he joined the army.
On 7 November 1933, he had been gazetted to be a Second Lieutenant with the 100th Worcestershire and Oxfordshire Yeomanry Field Brigade.
By the time of his marriage, he had transferred to the 1st Battalion the Duke of Cornwall’s Light Infantry which was based in India from 1922 to 1939.
He married Audrey Catherine Chaworth-Musters at Nottingham on 15 September 1938. Nine days, later, on 24 September, they embarked on the City of Simla on their way to Karachi. Two sons were born in Lahore, one in 1940 and the other in 1942. They lived at The Residency, Lahore.
The Battalion moved to North Africa in 1941.
Myles held the rank of Major when he was killed on 5 June 1942.
He is buried in Knightsbridge War Cemetery, Acroma in Libya.
On 17 December 1942, Audrey, arrived at Liverpool on the Franconia, with her two sons. She went to live with her parents at the home of her forbears, Annesley Park, Nottinghamshire. Her parents-in-law lived at Langtons, Farnham Common in Buckinghamshire. Her elder brother was killed in 1943. She died in 1982.