Gary Moore believed neither himself nor Sire De Grugy would ever have a better chance of a Grade One win than in the BetVictor Tingle Creek Chase and the chestnut lived up to his expectations up the Sandown slope.
Sprinter Sacre's absence had made this an immeasurably easier task, but the tricky fences along the back straight still stood in their way and Moore's son Jamie was put to the test.
But Sire De Grugy's tremendous cruising speed and determination prevented him from being boxed in on the tight run around the last couple of fences and a storming leap at the last gave the 7-4 joint-favourite enough breathing space to thwart the staying-on Somersby by four lengths.
Paul Nicholls sent out five winners on the day, with the biggest of a Daryl Jacob-ridden Esher treble coming through Hinterland (13-2) in the Racing Post Henry VIII Novices' Chase.
Second to Captain Conan in the race last year, this was only the chestnut's second victory over fences.
Nicholls' Saphir Du Rheu (8-1) bolted up in the Pertemps Network Handicap Hurdle, while There's No Panic (9-1) rounded off a terrific day at the Ditcheat office in the LDS Leak Detection Specialists London National.
Leighton Aspell performed arguably the escape act of the season as Deep Trouble (7-1) lived up to his name jumping the last in the Jumeirah Hotels & Resorts December Handicap Hurdle.
Nicky Henderson's Vaniteux (7-2) was quicker on the run-in than the Nicholls 6-4 favourite Vibrato Valtat in the David Johnson "National Hunt" Novices' Hurdle, with Nick Williams' good run continuing through Benefique Royale (12-1) in the "Hutch" Anniversary Anne Boleyn Mares' Handicap Hurdle.
Speaking after Sire De Grugy's victory, Moore senior said: "It means the world, it's what you get up for, and it just goes to show it doesn't matter what you pay for them, it doesn't always make them. He was cheap.
"A lot of top people passed him over but a lot of credit must go to Jamie, as he went and saw him and said 'you've got to buy this horse as soon as you can."
Sprinter Sacre could make his belated reappearance in the Desert Orchid Chase at Kempton over Christmas, and Moore believes it would be his only chance of beating the National Hunt great.
He said: "I'm going to have to take him on at some point and I'd rather it was at Kempton (Desert Orchid Chase, December 27). If I want to swerve him I can go to Leopardstown, but I'd say he'll go to Kempton.