Mary was born in 1922 in Buckfastleigh, Devon, and spent her childhood there. By the age of 20, while Mary was working for an accountant in Totnes, she was called up and joined the WAAF (Women’s Auxiliary Air Force). Mary was posted to RAF Coastal Command St Eval, Cornwall, where they provided anti-submarine and anti-shipping patrols off the South West coast. There she was secretary for Squadron Leader Shackleton, son of the explorer Ernest Shackleton.
Mary was then posted to the Air Ministry in the War Office in Whitehall. She worked as a typist for the Cabinet Cipher Office, which dealt with secret messages. This often involved typing up letters from Commander Lord Mountbatten, including letters to the King.