THE world’s best riders will be on show when the Fidelity Blenheim Palace International Horse Trials get under way today.

William Fox-Pitt, Zara Phillips, Pippa Funnell and Mark Todd are among those tackling one of Britain’s toughest eventing courses.

And this year, nations will compete for the first time to try and earn a team place at London 2012.

New Zealand, Japan and Australia have entered the team event, with the latter two yet to secure their spot in next year’s Olympics.

The higher placed of the two nations will join host nation Great Britain along with Canada, New Zealand, USA, Germany, Belgium, France and Sweden.

The dressage stage of the main CCI*** competition take place on Thursday and Friday, with the cross country event on Saturday.

The event draws to a close on Sunday with the show jumping.

There are other events for younger horses and riders over the four days, with more than 175 trade stands and a wide range of displays also taking place.

Car parking and entrance for accompanied under 12s is complimentary, with tickets available at the gate.