William Haggas and Tom Marquand enjoyed their winners of the meeting when Merchant stayed on stoutly to claim the King George V Stakes at Royal Ascot on Thursday.

Sporting the well-known colours of Highclere Racing, the unexposed three-year-old was sent off a 3/1 chance in the hands of Tom Marquand following his dominant success at York's Dante meeting.

Stepping up to a mile and a half for the first time, the son of Teofilo came with a late sweeping run down the centre of the track to strike the front in the closing stages, seeing off Aidan O'Brien's Serious Contender (7/1) by a length.

John and Thady Gosden's Pantile Warrior finished a further neck behind in third at odds of 40/1.

"Merchant did well today and is progressive. He likes a trip and doesn't mind the ground," said Haggas.

"I need to see it again, but he looked a bit fresh early. I think he's improving and that's what every trainer wants, a nice improving three-year-old. Who knows how far he will go, but he is going in the right direction.

"A lot of people don't understand what trainers go through. Yesterday the horse coughed 10 times at exercise, never coughed before. Then the seeds of doubt come in, the sleepless nights, are we doing the right thing, do I tell Harry [Herbert of Highclere Thoroughbred Racing]? No. Yes, we are doing the right thing, we must run, and the horse is fine.

"Then going into the saddling box, he slipped just as he was going in. He then held his leg – the left-hind – all through saddling, so we went out and trotted him up twice. He seemed alright, but I said to Tom if you're not happy with him at the start, take him out. We couldn't tell anyone; we've got 50 people here. It is not all plain sailing, so when they win, it is absolutely fantastic. I am thrilled to bits."

When questioned about publicising the above, Haggas said: "That is complicated. No one knows why he coughed, but he did, and when they don't and they suddenly do, it's a bit of a nerve-wracking situation.

"I have been doing it a long time; you take a decision, you stick by it, and it's paid off, so we can now drink another glass of sparkling water!

"I don't know whether the punters trust us, but I think the Highclere shareholders, Harry and his management team trust us. We will make a decision for the horse's benefit."