Having finished third on his debut, the Andrew Balding-trained colt was backed down to 7-2 favouritism and was always handily placed on the rail from his draw on the stands side.
James Doyle delivered Tactical with a telling run to hit the front well inside the final furlong and lift the Listed contest by a length and a quarter.
It was a double for Doyle, who had earlier won the feature Prince of Wales’s Stakes with Lord North.
Yazaman (20-1) stayed on late to snatch second place by a short head from Muker (40-1).
The Queen's bloodstock adviser John Warren said: "I think everyone involved is absolutely thrilled - all of Her Majesty's team, and obviously Andrew and his team.
"Throughout the conversations the Queen was saying how delighted she is to produce a two-year-old winner at Royal Ascot."
Looking to future plans, Warren said: "It looks like he will stretch out in trip, so we'll look at races like the Richmond at Goodwood and the Prix Robert Papin in France."
He added: "Andrew has been saying since the spring the colt was naturally precocious and was finding his work terribly easy. It looked as though he was a nice prospect, even if we didn't immediately clock him as an Ascot two-year-old.
"When he ran at Newmarket, he got himself into a little bit of trouble, but he had such a good introduction and came out of the race so well, it boded well for his prospects to come here.
"We debated long and hard whether to take him to the Coventry over six furlongs, which would have been his preferred trip, but he has plenty of pace and he did it well.
"It is obviously a great shame Her Majesty isn't there to enjoy the buzz of having a runner, but she has studied every bit of it today, watching the races. It's the icing on the cake to have a winner for her.
"I think the Queen, every day of her life, follows racing one way or another when she can. She will have read the Racing Post and known very well the important, fancied horses. She always dedicates half an hour or so to the information every day, so she's very well tuned in and racing is her tremendous pleasure.
"The Queen doesn't get frustrated lightly - she's very pragmatic and takes everything in her stride. I suspect deep down there may have been a tinge of disappointment she wasn't there, but that was completely overridden by having a winner and breeding it.
"I suspect she got a warm inner feeling from pulling this one off."
Doyle said: “I finished second on Magnetic Charm last year (in the Sandringham for the Queen) and I was absolutely gutted. I could have done things slightly different so to get it right today it does mean a lot.
“I’ve been lucky enough to meet Her Majesty at the gallops at Beckhampton and I’ve been lucky enough to ride quite a few winners for her now. To get her a Royal Ascot winner means everything.”
Balding said: "He was showing a fair bit at home before we ran him first time out and he ran a nice race at Newmarket. We were quite hopeful today, particularly when the draw looked like it would be more of a help than a hindrance.
"He would have been ready to run in April, which is very early for one of mine. He's got a great attitude and is very professional.
"I think he will be more comfortable over six furlongs. We looked at the Coventry, but felt it was a stronger race and decided he had enough pace to stick at five."
He added: "It's obviously a great thrill for all of us to have a royal winner at the Royal meeting.
"On racedays we tend to give the Queen a ring in the morning and give her our thoughts. We did that this morning, so she was well informed!"Last chance to get your free month trial of Racing TV! Every race live from over 80 meetings from some of the best British and Irish racecourses. Click here for more details.
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