Arnold was born in October 1915 in Leeds, Yorkshire to Lithuanian born Paul and Fanny née Rubenstein and had four siblings Nathaniel, Rita, Ronald and Joyce. Their father Paul became a naturalised British citizen in 1903 and was the managing director of Hipps Ltd, a large wholesale tailors in Leeds.

Arnold was the observer on Stirling N6018 which departed RAF Wyton on an operation to bomb Sequedin power station near Lille. The aircraft jettisoned its bombs on Dunkirk when the primary target couldn’t be attacked due to cloud cover. The aircraft was hit by flak. Arnold was killed along with crew members:
Sergeant S N Symondson
Sergeant D H Jeeves
Sergeant L O Orchard
Sergeant D H Eve
Pilot Officer J R Bushell

Sergeant G Armstrong and Squadron Leader T W Piper became prisoners of war.