Knight moved his string from his old base in Sussex during lockdown into Rathmoy Stables, recently vacated by David Lanigan.
Mark Johnston's Dark Vision, a Group Two winner as a juvenile, shot clear inside the final furlong and looked set to return to winning ways.
However, Ben Curtis, leading jockey on the all-weather through the winter, had yet to ask for everything on Sir Busker.
William Knight told us about his stable move on Luck On Sunday last month
Having been momentarily outpaced, Sir Busker picked up well and won going away by a neck.
The winner is owned by Kennet Valley Thoroughbreds and among the winning syndicate is Arena Racing Company executive Martin Cruddace.
Kennet Valley's Sam Hoskins said: "We're delighted, it's so nice for the owners who have been very patient, he was supposed to be going for the Lincoln but obviously that was never going to happen.
"I'm so pleased for William, too, to get his first winner from his new yard, it's an emotional day."
Hoskins added: "Hopefully he might go to Royal Ascot now, for the Hunt Cup or something.
"He progressed quietly last year and he's at his best on a straight track. A race like the Balmoral at the end of the season might be perfect for him. I never thought I'd be so excited about having a winner at Newcastle!"
Hollie Doyle wasted no time in picking up from where she left off before the lockdown as Canagat showed plenty of determination to hold on in the Betway Casino Handicap Stakes.
Doyle rode over 100 winners in 2019 and was in fine form before racing was forced to shut down due to Covid-19.
She had formed a fruitful partnership with Archie Watson and the two young guns look set to be profitable to follow in 2020.
Canagat (3-1 favourite) won on his second of two outings last season and given he was blowing plenty in the paddock afterwards, he looks sure to improve for the run also.
Despite looking like being swallowed up a furlong out, with the rail to help he stuck to his task gamely to win by a neck and the same from Ayr Harbour and Jean Baptiste.
Doyle said: "It's good to be back in action and get a winner under my belt.
"Canagat was very gutsy. I thought the (Mark) Johnston horses (Overwrite and One Hart) weren't going to let me have it easy, so I let him cross over to the rail and it gave him something to aim at.
"The stamina really kicked in, he stays a lot further. He's a big unit and there's more to come."
Sir Michael Stoute has made a good start to the season and followed up a winner on the first day when Mubakker took the Heed Your Hunch At Betway Handicap.
Unbeaten on the all-weather, the Sheikh Hamdan Al Maktoum-owned four-year-old defied a mark of 95 in style, suggesting there are good prizes to be won with him.
The 7-4 favourite beat the 100-rated Glen Sheil by two and three-quarter lengths.
Jockey Dane O'Neill said: "I think Mubakker did it well in the end. It's riding a bit slow and he was a little rusty in behind them early, they were going a nice gallop, but he picked up well in the end.
"They weren't stopping on the front end, they haven't been, so I was conscious of that and he's been off a while. You're trying to do two things at once, you're trying to ease him into the race and you're trying to win your race at the same time, but I thought it was a pleasing performance and he can build on that.
"The only time he has disappointed on grass was on soft ground and on his breeding you'd suggest that if he's to go on the turf he'd want a sounder surface."
Select any odd to add a bet