Irish trainer Dermot Weld has ticked off a glaring omission on his glittering CV with Harzand giving him his first Epsom Derby.

Weld has won many races around the world including two Melbourne Cups.

He became the first northern hemisphere trainer to win Australia's most famous race with Vintage Crop in 1993 and claimed it again with Media Puzzle in 2002.

In what was billed as one of the most open Derbys in recent years on Saturday (Sunday AEST), Harzand gave his owner the Aga Khan a fifth win in the famous race.

While there were plenty of celebrations in the wake of his triumph, the 13-2 shot nearly missed his engagement in the race after spreading a plate in the build-up.

He was eventually given the green light and went on to lead in an Irish trifecta with the Aidan O'Brien-trained US Army Ranger and Idaho second and third.

"It's very special to win this race," Weld said.

"I think I've had 23 Classic winners in Europe. Blue Wind was my first when she won the Oaks many years ago (in 1981). I've won a couple of Irish Derbys (Zagreb in 1996 and Grey Swallow in 2004) but I've always obviously wanted to win this race.

"I've possibly never had a horse good enough to do it, but today was the day.

"We had a huge worry this morning as he spread a plate travelling over and he was a very doubtful runner right up to about an hour before the race.

"But with the tremendous help of all my colleagues and my team, we made it."

Harzand could face a rematch with the four horses that followed him home in the Irish Derby later this month.