Defending champion Stuart Hayes returns to this year’s Blenheim Triathlon tomorrow looking to make it three-in-a-row.

He will be out to fight off the challenge of 2006 world champion and four-time British national champion Tim Don.

The two triathlon heavy-weights will go head-to-head alongside 5,500 competitors comprising elite athletes, first-timers and relay teams.

The UK’s second largest triathlon, set in the palace’s stunning surroundings, will be watched by an estimated 15,000 spectators.

London-based Hayes is aware of the threat posed by Don. He said: “Tim is a world-class athlete and currently ranked ahead of me, so I will have to be at the top of my game to beat him.

“My hope is to continue my recent good form as I look to build towards my ultimate dream of gold at London 2012.”