The 2014 Commonwealth Games champion at 400 metre individual medley, he was part of the Great Britain 4 x 200 metre freestyle relay team that won gold at the 2015 FINA World Aquatics Championships, and silver at the same event at the 2016 Summer Olympics.

Competing for Scotland at the 2014 Commonwealth Games held in Glasgow, Wallace won the gold medal in the men's 400-metre individual medley with a first-place time 4:11.28.

[3] He was born in Edinburgh, and trained under head coach Laurel Bailey at Warrender Baths Club.

[4] At the 2015 World Aquatics Championships in Kazan, Russia, Wallace won a gold medal as a member of the first-place British team in the men's 4×200-metre freestyle relay.

On 11 April 2018, after winning two Bronze medals at the 2018 Commonwealth Games in Australia, Wallace announced his retirement from swimming at the age of 24.