Event rider Simon Grieve is on the sidelines for three months after being diagnosed with a rare type of deep vein thrombosis.

Simon was competing at Poplar Park on 27 April when he noticed that his right arm was starting to hurt.

“When I pulled my gear off, my arm was three times its normal size,” he told H&H.

“A paramedic thought it was a blood clot, but I went to A&E and they pretty much turned me away. My GP said it would go down, so I carried on as normal.”

But Simon’s arm grew increasingly uncomfortable and at Chatsworth earlier this month, Team GBR physiotherapist Andy Thomas urged him to have it checked out immediately.

He was diagnosed with Paget-Schroetter disease, a form of deep vein thrombosis (DVT) in which blood clots form in upper body.

In Simon’s case, the DVT had formed in the vein between his collarbone and first rib.

“I could had a heart attack or a stroke and dropped down dead at any moment,” said Simon.

“I feel incredibly lucky.”

He spent a week in hospital and is now back home at his yard in Tilton-on-the-Hill, Leicestershire.

“I feel absolutely fine in myself, but I am on the blood-thinning drug Warfarin for three months, which means I can’t compete.

“If I were to have a bad fall, the blood wouldn’t clot properly,” Simon explained.

Terry Boon and Lucy Crocker are coming in to ride his horses, and Simon hopes to have the all-clear in time to give his top string, Cornacrew, his pre-Burghley prep runs.

He is using the time out of the saddle to work towards his coaching exams.

“My owners are being amazing,” he told H&H.

“I feel privileged to have such fantastic support.”