Australian Group One winner Merchant Navy has won the Diamond Jubilee Stakes at Royal Ascot for new trainer Adian O'Brien.

Sent off at 4-1, Merchant Navy was all out at the line under Ryan Moore but managed to hold out French raider City Light by a short head.

American runner Bound For Nowhere finished third with the race marred by controversy when favourite Harry Angel was declared a runner despite having his leg caught on the side of the stall and missing the start.

O'Brien said Merchant Navy, winner of the Coolmore Stud Stakes at Flemington last spring, could run in the July Cup before he returned to Australia for stud duties at Coolmore.

"He was travelling very well and we knew looking at him that Ryan was very happy on him," he said.

"I think Ryan was hoping not to get there (the front) too early on him and then he got a little bit of a bump and Ryan said it took him a bit of time to re-balance."

"We thought it was an impossible task for him here as he was 12lb (5kg) worse off than he would have been in Australia.

"He's being treated as a four-year-old here and he's really a three-year-old. I came here prepared that he couldn't win, reading what everyone was saying."

"The plan was that he'd run here and then go back to Australia, as I think there's a lot of mares waiting on him there."

Australia's other runner, Redkirk Warrior, finished out of the placings.

Harry Angels' trainer Clive Cox said the horse had come out of the barrier incident the worse for wear.

"His leg was still in the stall when it opened," Cox said.

"He's got a nasty puncture wound, which we're concerned enough about. He wasn't sound behind when he came in. Not dreadful, but he wasn't sound.

"I'm just sorry for everyone and it's a shame, but I hope he'll be fine."