John Arundel Theobalds was born in 1902, son of Dr. Arthur John Arundel Theobalds, M.D., and Effie Theobalds and was husband of Dorothy (Thea) Theobalds, of Fleet, Hampshire.

He was educated at Wellington College, Berkshire, before passing on to Sandhurst. In 1921, he was commissioned in to the Oxfordshire and Buckinghamshire Light Infantry.

In 1936, John was seconded to the Royal Air Force - and was to remain with them until September 1941.

Following this, he was made Second in Command of the 2nd Battalion of the Durham Light Infantry. The regiment travelled to India in 1942 and that August, John was placed in overall command.

In March 1943, he was awarded the Distinguished Service Order for his conduct during operations at Donbaik:
"He suddenly found himself in command of the Brigade at India after the capture of the Brigade Commander and faced with the most difficult task of withdrawing the Brigade to Kyaukpandu in the face of strong enemy pressure. The success of this operation was entirely due to the plan made by Lieutenant-Colonel Theobalds. He has been throughout an inspiration and example to his battalion."

In 1944, he was appointed to command an infantry brigade for the relief of Kohima.

He was wounded on 14 May while making a personal reconnaissance from a forward trench and died two days later on 16 May 1944, he was 42 years old.

John is commemorated in Imphal War Cemetery, India in plot 7.G.23.