Returning to active service by October 1940 he commanded 229 Squadron from RAF Northolt for the last 12 days of the Battle of Britain.

In November 1941 he spotted an Australian Tomahawk aircraft being forced down by enemy fighters and landed his single-seater to rescue the pilot.

Having got Sergeant Burney aboard, he attempted to take-off but suffered a burst tyre and crashed the aircraft.

Both he and Burney walked across the desert for four days, avoiding large enemy patrols, to reach safety with a Guards unit.

He was appointed Officer Commanding RAF Horsham St Faith in 1947 and then went on an Exchange Officer posting with the United States Air Force in 1948 and on return to the UK was appointed an instructor at the Joint Services Staff College in 1950.

Rosier was advanced to a Knight Grand Cross of the Order of the Bath in 1972, before he retired from the RAF the following year.