Born in 1918, Grayburn was educated at Sherborne School in Dorset and joined the Army Cadet Force before the outbreak of the Second World War. He was initially commissioned into the Oxfordshire and Buckinghamshire Light Infantry and later joined the Parachute Regiment. At the age of 26 he went into action in the Battle of Arnhem where he was part of the small force that was able to reach Arnhem road bridge. Between 17 and 20 September he led his platoon, and later the remnants of a battalion, in the defence of the small British perimeter around the bridge, but was killed after standing up in full view of a German tank in order to direct his men to new positions.