Thousands of triathletes endured blistering heat to swim, cycle and run around Blenheim Palace.

Temperatures which soared to 26 degrees Celsius today, helped draw crowds of 15,000 people, but made the event even more gruelling for competitors.

The fourth triathlon at the palace attracted 5,500 racers, made up of elite athletes and a crop of first timers.

Jo Delo, 18, of Lower Radley, was taking part in his first first triathlon.

He said: "It was a great event. Even if the supporters don't know you, they still cheer you on."

The teenager had completed the 750m swim, 20km bike ride and 5km run in about two hours.

"It was a bit slower than I had hoped, but I am happy and was glad my parents and girlfriend were there to watch me," he said.

Simon Balderson, an IT teacher at Abingdon School, is currently setting up the school's first triathlon club.

The 26-year-old believed he had beaten last year's personal best of one hour and 20 minutes.

He said: "I have come eighth in my group, but not sure overall. I have not had my time confirmed yet.

"It was a fantastic event - incredibly well organised and a great set-up. The swim was the hardest part, but I did better than I thought. Today's event was also the launch of our school's triathlon club.

"Both the boys and staff have been very enthusiastic."

Mr Balderson was joined by history teacher David McGill.

The 35-year-old, of Mayotts Road, Abingdon, said: "This was my first triathlon and I would like to do another one soon.

"I enjoyed it so much. My wife Elizabeth, seven-month-old daughter Isla, and sister Anna, were watching at various stages around the course, spurring me on.

"I nearly crashed off my bike as I waved to them!"

Families, couples, pensioners and children enjoyed tucking into picnics and ice creams as they sat cheering and applauding the men, women and youngsters, as they finished their exhausting races.

Oxford Tri Club member Rachel Stoakes, of Tetsworth, near Thame, finished fifth in the elite women's race.

The 24-year-old said: "This was my first triathlon at Blenheim.

"My aim was to come in the top five and I am glad I fulfilled it.

"I completed in one hour 13 minutes and 45 seconds. The atmosphere was awesome. It's very inspiring."

Event director Nick Rusling said it had been a privilege to be at the event.

The 34-year-old said: "My highlight is always standing at the finishing line watching people's faces when they realise they have done it.

"It is a spectacular event - every year it keeps getting bigger and better."