David Davies first came to attention at the 2002 Commonwealth Games where he took nearly a minute off his personal best to finish sixth in the final of the 1,500 metres. He was European junior champion in 2003 and then marked his emergence into true world class by breaking the 15-minute barrier for the 1,500 in early 2004. He was the fastest qualifier for the Olympic final and contended for the gold before fading into third. Between Athens and Beijing he was a regular medal winner at the major championships and won bronze medals at both the 2005 and 2007 World Championships. With Olympic champion Grant Hackett absent through injury, Davies won the 1,500 freestyle at the 2006 Commonwealth Games in Australia and added a bronze in the 400 free. After winning a silver medal at the European Championships early in 2008, Davies decided to add open water swimming to his schedule in an attempt to double up at the Beijing Olympics and he qualified in only his second race at the 10 km distance. He reached the final of the 1,500 m indoors and was then involved in an epic race in the open water event. Davies, Thomas Lurz and Maarten van der Weijden broke away from field and contested the medals between them. Davies led the race but in the final sprint veered off course which allowed the Dutchman, van der Weijden to power home for victory. Davies was exhausted and delirious at the finish and had to have medical treatment. After two years in which he remained a contender though without actually adding to his medal collection, Davies suffered a collapse of form in 2011, before making it onto the British team for the London Olympics but failed to make the 1,500 final. Three months after the London Games, Davies announced uis retirement and took up a position as an athlete mentor with project Sport Wales.