Progressive stayer Limestone (10/3) continued a strong spell for trainer Joseph O’Brien as he scored by the narrowest of margins in the Group 2 Queen’s Vase at Royal Ascot on Wednesday.

Limestone was pushed along early in the straight by Dylan Browne McMonagle, but his stamina kicked in and he finished strongly to deny the closing Del Maro (12/1) by a nose. Front-runner Ranga Tang (40/1) was a length further back in third.

A winner in listed company at Navan on his previous start, Limestone has now won four races on the bounce, with the son of New Bay also taking minor contests at Listowel and Cork.

O’Brien said: “The horse is very tough and tenacious. It was a close finish, but I am delighted to come out on top. I thought we were beaten to be honest. Dylan gave him a fantastic ride. He got a great spot and control of the race, which is what we intended to do because we felt our best attribute was a little bit of speed.

“He ran down the straight and we were coming there. I thought the Godolphin horse might have just nabbed us, but our fellow has been in a couple of photo finishes through his career and he comes out on top, so it is a good trait to have in a racehorse.

"I think the sky is the limit for him in terms of a middle-distance or staying horse. He has got better with every race and has an outstanding pedigree. He is a son of New Bay who has improved with every start, so all we can do is see how far he can climb.”

Browne McMonagle said: “I was very happy going into the first turn. Limestone pinged the gates and I rode forward. I had my options open. If there was a couple going, I was happy to follow, but if there was no speed, I was going to let him stride because he is a big galloper with a lovely cruising speed. It worked out well when a couple took it off us, giving me a lead.

“I felt I was in the perfect spot, especially as we didn’t go overly quick, and it gave me something to run at. They quickened off the bend, which caught me for a little bit of pace, but I knew this lad would come in the last furlong and we’d hit the line strong.

"He is a very tough horse, this fellow, and he is improving with every run. He is always winning by margins, always doing enough, and that is what you want with these kinds of horses that are going to stay. Horses that just do enough keep progressing. He is definitely one of them.

“A big well done to the team, a second winner of the week. The horses are in great order and there are plenty of nice chances for the rest of the week, so hopefully we are not done yet.”

Del Maro’s trainer Charlie Appleby said: “We are getting closer! He is a nice staying type. His pedigree is what it suggests, that he will stay, and we rode him to come home and he has done it. You will have to treat him as a potential St Leger horse, yes.

"You could question how much he tries on some of his runs, but he has tried there. For me, he is a nice horse because that is one thing we do not tend to have too many of – stayers – so I will have to start training him like a stayer. A winner would be nice, but we will keep going.”

John Gosden said of Royal runner Point Of Law, who finished fourth: “Not a great run from the first bend – he got hit hard from the inside and outside, which knocked him back to last. He showed a great attitude and stayed on very well. A nice horse for the future. He will learn."