Aidan O'Brien opened his account for the week, as did Ryan Moore, with a hard-fought success from Power in the Coventry Stakes at Royal Ascot.
Sent off the the 4-1 favourite having won his previous two starts, he was well behind in the early stages, but as the pacesetters - which included American raider Italo - began to weaken, the unbeaten colt began to find his stride.
Roman Soldier hit the front under George Baker and the pair came together inside the final furlong, prompting a stewards' inquiry, but Power was a neck ahead at the line and kept the race.
O'Brien said: "Ryan gave him a great ride and he's a tough horse. It's tough out there. He won his maiden over six furlongs at the Curragh and then won the Marble Hill over five furlongs.
"He's a big, powerful, strong horse and he has the physique already. Most horses at two have to progress, but he has it already.
"I spoke to Ryan on the way in and asked him if he would stay further and he said no problem. All things are open to him. He could go back to the Phoenix Stakes at the Curragh. Looking at him you'd think he'll get further.
"It's a relief for everybody (to have a winner). Everyone works very hard and puts a lot into it. It's great to have a winner here - it's a very special meeting."
Jeremy Noseda, trainer of Roman Soldier, said: "So close, yet so far. He's run a huge race so I can't ask any more than that. It was a lovely ride by George (Baker) and a brave performance by the horse. That's all we can ask. George said he got a little bump, but I don't know."
Brian Meehan, trainer of the third St Barths, added: "He's very progressive. Martin (Dwyer) said he was very unlucky at the start. He had to take a pull back and go round, so he possibly could have finished a bit closer, but whether he would have troubled the first two I don't know. We're delighted."