Un De Sceaux lived up to the pre-race hype by winning the Sodexo Clarence House Chase at Ascot in style.
The 1/2 favourite put his latest fencing blip behind him and jumped with poise throughout, a fast jump at the third-last fence stretching out his rivals before the home turn.
Sire De Grugy (11/4) and Jamie Moore gave their all and got to within half a length of the leader two out, but Walsh let out a little rein, flew the last and accelerated away up the run-in to score without having to be asked for maximum effort.
Sire De Grugy had to work hard to hold off the challenge of stablemate Traffic Fluide for second place, but the pair were no match for the five-length winner, with Vibrato Valtat appearing to run his race another three or so lengths back in fourth.
Asked to compare the winner to former two-mile greats with whom he has been associated, Walsh said: "I don't know, he has to win a Champion Chase before I can say that.
"I was lucky enough to ride Master Minded and Azertyuiop and rode against Moscow Flyer, so I've ridden some great horses, but he has all the attributes - he stays really well and has a good turn of foot."
Walsh, in common with most onlookers, had reached the conclusion that, if anything, the horse's fall on his previous start at Leopardstown had actually helped him here.
"He was definitely looking (at his fences) a bit more today than he did at Leopardstown, which is probably no harm," said the rider. "A good round of jumping like that will give him confidence.
"Today was important, with such a good horse you want to be winning these big races and with it going wrong in Leopardstown it is great to come and do that."
Mullins added: "He jumped much better today, he seemed to measure all his fences. I'm hoping he'll improve a lot from that.
"He's full-on every day, like he is racing, but he appeared more settled today than I've ever seen him.
"I think I'd rather watch him if he was someone else's! When they're your own and you have so much invested in them and they are jumping flat out, it makes your heart jump every time."
"It's all or nothing with him," winning owner Ed O'Connell told Racing UK. "You're dealing with a masterclass from Ruby. He was fantastic today - I thought it was probably his best performance ever. He got in close to a couple but he shortened and fixed himself. A lot of today is down to the work that has been done with him."
Gary Moore, trainer of the runner-up and third, was magnanimous in defeat for 2014 Champion Chase winner Sire De Grugy.
"He's obviously been beaten by a very good horse," said Moore. "He took the sting out of us with his frontrunning, relentless gallop. We'll have to go for the Champion Chase - there's nothing else for him. We'll take him home, freshen him up, and do our best."