On 8/9 April 1944 at the Battle of Kohima, British India, Lance-Corporal Harman was commanding a section of a forward platoon where soldiers of the Imperial Japanese Army had established a machine-gun post within 50 yards of his company and were becoming a menace. Since it was not possible to bring fire on to the enemy post the lance-corporal went forward by himself and threw a grenade into the position, destroying lieutenant He returned carrying the enemy machinegun as a trophy.
Early next morning, having ordered covering fire from his Bren gun team, he went out alone, with Lee–Enfield and fixed bayonet and charged a party of Japanese soldiers who were digging in.
He shot four and bayoneted one. A plaque is displayed on the house where he was born in Shrewsbury Road, Beckenham, located in the London Borough of Bromley.
There is also a memorial to him erected by his father in Venture capital Quarry, on the east side of Lundy Island.