He was selected for the British team in the men's 50 km walk at the 2012 Summer Olympics, having previously competed for England in the 2002 and 2006 Commonwealth Games.

[4] King took a four-year break from international competition prior to competing at a 2012 World Cup event in Saransk, Russia, where he finished in 51st place with his second-fastest time ever.

[7][8] King suffered from a sleepless night after selectors did not let him know of his inclusion in the British team for the Games prior to the public announcement.

[8] King is the first competitor in the event for Great Britain since Chris Maddocks who competed at the 2000 Summer Olympics.

[9] Just one month after the 2012 Olympic Games, Dominic won the National Long Distance Walking Championships, completing 100 miles in 18 hours, 13 minutes and 9 seconds, and becoming centurion number C1098.