Born in London to London-born, Edinburgh-trained artist Keeley Halswelle and Helen Marianna Elizabeth Gordon, he is nonetheless usually referred to as being Scottish, the nationality of his maternal grandfather, General Nathaniel J.

[2][3] Wyndham Halswelle had a notable athletic career at Charterhouse School and the Royal Military College, Sandhurst, before being commissioned into the Highland Light Infantry as a second lieutenant on 8 January 1901.

[1] Serving in South Africa in 1902 for the Second Boer War, Halswelle's ability was recognised by Jimmy Curran, a coach and amateur athlete.

On his return, in a single afternoon in 1906 at the Scottish championships in Powderhall, he won the 100, 220, 440 and 880 yards races (91, 201, 402, 805 m), a feat that has not been matched since.

While blocking competitors was an acceptable strategy in the United States, it was prohibited by the British rules under which the 1908 London Olympics were organised.

He was also under pressure from his senior officers, who felt he was being exploited,[9] and he retired from athletics after a farewell appearance at the 1908 Glasgow Rangers Sports.

[1] Halswelle, by then a captain, was killed by a sniper at the Battle of Neuve Chapelle in France, during World War I,[1][10] on 31 March 1915 aged 32 while attempting to rescue an injured fellow officer.

Earlier in the same battle (12 March) he was hit by shrapnel or shell fragments while leading his men across an area known as Layes Brook but despite his wounds he refused to be evacuated and continued at the front, although heavily bandaged.