Listen to the clips below of competitors' thoughts from 2015 and previous years.
William Fox-Pitt goes clear inside the time on his 2nd horse Freddie Mac. An amazing recovery means they stay on score of 38.0.
Last year's CIC3* winner Fernhill Pimms opens up with 35.8 for William Fox-Pitt in the CCI.
Francis Whittington is happy enough with his score of 37.2 with Easy Target.
Andrew Hoy completes a brilliant test on Friday with a score of 34.0.
Cross Country Course Designer Eric Winter discusses the challenges ahead over the weekend.
Blenheim first timer Lydia Hannon from Watlington is disappointed with her score in the Dressage.
A personal best by Blenheim debutant Emily King. She takes the lead on day 1.
William Fox-Pitt lies in 2nd and 3rd with Freddie Mac and Seacookie.
Carl Hester talks about the recent success for British Dressage at the World Equestrian Games on his visit to the Blenheim Palace International Horse Trials.
Excellent start for Francis Whittington and Fernhill Highlight with 43.4 in the Dressage.
Blenheim Palace Horse Trials Office: Blenheim Palace, Woodstock, Oxon, OX20 1PS Tel: 01993 813335