[3] Stallard was educated at Sherborne School (1914–1919), an independent school for boys in Sherborne, Dorset, before going up to Gonville and Caius College, Cambridge, where he studied medicine,[4] and was a contemporary of Harold Abrahams.

[7][8] Additionally, he was part of the Oxbridge team that set a world record in the 4×880 yd relay in 1922.

[11] Stallard competed at the 1924 Summer Olympics held in Paris; he won the bronze medal in the 1500 metres (time 3:55.6) and finished fourth in the 800 metres (time 1:53.0), despite sustaining a stress fracture in the right foot in the 1500 m heats.

He was portrayed by Daniel Gerroll in the 1981 Oscar-winning movie Chariots of Fire.

He withdrew at the last minute from the 1926 AAA Championships after a copious blood donation to a patient at his hospital.