David Simcock's horse, so often on the fringes at the top level, came with a storming late run to beat Zonderland by a nose to take this Group Two prize.
It was almost a carbon copy of 2016, in which the same two horses filled the first two places, only this time Lightning Spear was made to work extremely hard by his old rival.
It looked as though the race was going to go the way of last year's runner-up Zonderland on his long-awaited return, after the Clive Cox runner reeled in leader Hathal late on.
But in one final swoop the even-money favourite pipped Zonderland on the post, winning by a nose.
Winning rider Oisin Murphy said: "I just about got it right. I made no secret about how tactical the race was going to be. It was impossible to know what was going to happen, but you have to have confidence you have chosen to do the right thing and thankfully I just about got it right.
"Fair play to Sheikh Fahad and David Simcock for persevering with the horse. They got him here in tip-top shape after a heavy ground performance in the Sussex. It was a good performance today.
"I've lived, breathed and dreamt horse racing since I was a child. It's very hard to leave it at the races. Lads say they can leave it behind when they go in the door, but I can't so it's important when it goes right."
David Redvers, racing manager to Sheikh Fahad's Qatar Racing operation, said: "We sponsor the race at Ascot (QEII), but I imagine the Foret (at Chantilly) is a strong possibility. I believe he has a Group One in him and we've always believed he has."
Cox said: "It was close, but he has run a blinder after a year off. I'm pleased with the performance he put up. From where I was I hoped we had held on, but it was a bit like yesterday with the angles at York and sadly we were second.
"He has run a blinder and credit to my team as it has been a long year. I'm thrilled he is back here in good nick. I hope he will go to Ascot. It is a shame he was second, but credit to the winner."
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