The weather forecast might not be glorious - but that won't deter the 4,000 competitors expected to swim, cycle and run around Blenheim Palace this weekend for the third Blenheim Triathlon.

The event, held at the Duke of Marlborough's World Heritage site in Woodstock and this year sponsored by Mazda, will be the second largest event of its kind in the country and promises to be bigger and better than before.

Channel 4 will be televising the event again, as it did last year.

Racing gets under way at 10am on Saturday and continues throughout the day until about 4pm, while on Sunday the first race starts at 9am.

Triathletes will be competing over two distances, the sprint - 750m swim, 20km bike ride, 5km run - and the supersprint - 400m swim, 13km bike ride, 2.5km run - with other events such as elite races, team relays and an Oxbridge Varsity match also taking place.

Triathlon managing director Nick Rusling said: "It has been a hectic week, but we are really looking forward to welcoming all competitors to Blenheim for the third triathlon here. We are hoping and praying for good weather and really hope it improves."

Sunny spells and temperatures as high as 21C are forecast for tomorrow, but rain is expected on Sunday.

Last year, despite bad weather, 10,000 spectators packed into the palace grounds to cheer on friends and relatives.

Mr Rusling added: "The Blenheim Triathlon provides the ideal start to the triathlon season and is one of few triathlons to have such a stunning backdrop. It's a great starter race for anyone interested in the sport and, as always, there will be a huge number of first-timers taking the plunge at Blenheim this weekend."

One of those first-timers will be the Oxford Mail's digital content manager Malcolm Bradbrook, who entered this year's race after "chickening out" in 2005 and 2006.

He said: "The Blenheim Triathlon is something which I wanted to do in previous years but never quite got around to entering. This year, though, I've finally signed up and have been training hard. I'm quietly confident and my aim is to just get round. I have no idea of how fast or slow I'll be and am just going to enjoy it."

Malcolm has been swimming two or three times a week, commuting to work by bike covering 12 miles a day and running between 20 to 30 miles a week to prepare himself for race day.

He added: "I've dusted off my old Peugeot road bike and have been lucky enough to receive kit such as a tri suit and an Orca wetsuit from triathlon store Swim Bike Run. I'm really looking forward to putting it all to the test."

See oxfordmail.net on Monday for results and full coverage of the event