Muteela stretched her perfect record to four with a game victory in the Sandringham Handicap at Royal Ascot.
Mark Johnston's filly had progressed from a winning reappearance at Beverley to follow-up at Newmarket and took another step up in class - as well as a rise in the weights - in her stride.
Jumped out in front by Paul Hanagan, she was given an uncomplicated ride from the front and that certainly paid dividends with the runner-up having to come all of the way around the field from last place, failing by a short-head to get up.
Spencer's cause wasn't helped by the field merging into one group as they had in the preceding Royal Hunt Cup but nothing should be taken away from the winner who was in the vanguard through out.
It appeared as though the Dansili filly would be swamped inside the distance but she dug deep into her reserves to see off the challengers and gain a deserved success to the delight of the racegoers who helped send her off the 9/2 favourite.
There was a further half length back to Wee Jean in third with Graceful Grit close up in fourth.
Hanagan said: "To be honest, I wasn't that confident we'd won, because the second horse was quite away from me. Jamie (Spencer) said well done to me when we were pulling up, so that was enough for me.
"It would have done her good if the second horse had come to her, as she was on her own the whole way with no company.
"Every race she's run she's up there with the pace. She wouldn't really quicken, but she's very genuine and keeps galloping all day. We had a little fall out at Chester (earlier in the season) when I fell off her, but she's none the worse for it."
Johnston said: "She's very fast and there would be a slight debate about whether we should go back to seven furlongs, but there are so many opportunities at a mile and we've had this race in mind for quite a long time, so it's great to do it.
"We thought when she has run before that she needed every inch of a mile but the dam injects so much speed.
"Everyone was asking whether we were disappointed to get an 8lb rise for winning at Newmarket last time, but she needed that to get a run here.
"It's a tremendous family. I trained the dam (Nufoos) and I trained the half-brother Awzaan who won the Middle Park. She took a while to mature and grow up, but we knew this was on the cards.
"It's so hard to get a winner here, we didn't manage to get one last year so it's a great relief. I entered her in the Falmouth Stakes yesterday. As she has won over that course and distance, it would be very tempting."
Muteela was Johnston's first winner at the meeting since 2012 and he expressed his relief at getting on the scoresheet.
"You always have relief at Royal Ascot. It is so hard to have a winner, we didn't have one last year and we have had very few blank years so it is a relief to get one on the board having not had a winner since 2012," he added.