Odds are, That’s an Ironic Nickname
Sergent Len “Happy” Knox, 2nd New Zealand Division, 2NZEF, cleans an old-school .455-caliber break action Webley revolver Maadi Camp, near Cairo, Egypt, around 1940-41.
2NZEF would spend all of WWII under the British Eighth Army, seeing the elephant in Greece and at Crete, the fighting at Minqar Qaim and El Alamein; and the end of the North African campaign. They then crossed the Med and fought up up the Sangro and Monte Cassino across central Italy, finishing the war on the Northern Adriatic.
By which time, Happy was probably ecstatic.