Diminutive mare Headley Britannia has been put to sleep at the age of 21 after an accident cross-country schooling.

Ridden by Lucinda Fredericks, the 15.3hh mare won all 3 Rolex Grand Slam events — although not consecutively — taking Burghley in 2006, Badminton in 2007 and Kentucky in 2009.

She amassed 1,479 British Eventing points during her career.

“We were cross-country schooling in the beautiful sunshine and she was being ridden by Alexandra [Smith, Lucinda’s working pupil] who has been riding her for 5 months,” Lucinda told H&H.

“She was going brilliantly, we had jumped about 20 fences, and then she landed on perfect ground over a small jump and she just crumbled.”

Brit broke her radius bone in her left fore and a vet was called to put her to sleep.

“I am so grateful that I had about 20 minutes so say goodbye to her and thank her for everything,” Lucinda added.

“Amazingly she stood up and we took her saddle off and popped a rug on her. She was staring into the distance and it was a really personal moment between us.

“She was so calm and a complete professional until the end.”

Brit was retired from the top levels of the sport in 2012, but went on to win the CLA Game Fair Express Eventing competition last July.

Last month she competed at Aston-le-Walls unaffiliated horse trials finishing 9th in the intro class with Alexandra.

“Alex had been riding her so beautifully. I was so proud of how she and Brit clicked,” Lucinda said.

Brit was cremated this morning.

“We are going to place some of her ashes in the garden and plant a tree,” Lucinda said.

“We are going to take the rest up to Salisbury Plain and allow them to blow around free up there.”