Walter Swinburn, who rode Shergar to a landmark victory in the 1981 Derby, says he will never forget the best race of his life.

It will be exactly 20 years on Saturday since Shergar vanished in mysterious circumstances.

But his awesome victory in the 1981 Derby will be remembered as it was the biggest winning margin in the race's long history.

Swinburn says he feels privileged to have a played a part in the race that became the stuff of legend.

He was a great loss, even to people who didn't know him Walter Swinburn

"I was a 19-year-old boy having my first ride at Epsom," he said.

"It was a big, big occasion for me and the horse, but anyone could have ridden him.

"He took the day in his stride and that helped me."

Shergar might have been one of the most impressive Derby winners ever, but he is destined to be better remembered as the equine equivalent of Lord Lucan.

Swinburn says he can still remember hearing the news that Shergar was missing.

"It was obviously a terrible shock, we couldn't believe it," he said.

"It had never been heard of - that sort of thing - let alone for it to happen to a horse like that, that we were all so close to."

The kidnap made front-page news and the conspiracy theories began.

Stories circulated claiming that the horse had been spirited off to a stud in the Middle East.

Another rumour was that the horse's sperm had been extracted and sold.

Shergar's Derby win

Start: Swinburn gets his mount into a good position as soon as the gates go up. Halfway point: Shergar lies in third. Tattenham Corner: Most of the runners are off the bridle while Shergar is cantering. Three furlong marker: Swinburn coaxes Shergar into the lead. Final furlong: Swinburn has time to look round before Shergar crosses the line 10 lengths clear.

The syndicate, who bought shares in Shergar when he was put out to stud, issued a report blaming the IRA for the kidnap.

Twenty years on and there is still no conclusive proof of what happened to Shergar.

But there is no doubt that Shergar lives on in the memory as a barometer of greatness.

"Apart from being an outstanding racehorse he had an outstanding temperament," remembered Swinburn.

"You don't always get the two in racehorses.

"He was a great, great loss to a lot of people, even to people that didn't know him.

"If I go back to Ireland there is hardly a week goes by without someone asking me about him."