Sprinter Sacre continued his return to form with a thrilling win over Sire De Grugy in the Desert Orchid Chase at Kempton.
The 2013 Queen Mother Champion Chase winner, ridden by Nico de Boinville, last month had his first win since heart problems threatened his career.
Challenged by the 2014 Champion Chase victor, the 8-11 favourite had to work very hard to claim victory.
But a strong jump at the last saw him win by three-quarters of a length.
After being pulled up in this race two years ago, the Nicky Henderson-trained nine-year-old was later diagnosed with an irregular heartbeat.
But a win last time out at Cheltenham showed he was on the way back and as Sprinter Sacre drew alongside Sire De Grugy with four fences to go, the race started in earnest.
Sire De Grugy looked strong under Jamie Moore, son of trainer Gary, but Sprinter Sacre was not to be denied. Vibrato Valtat finished third.
Henderson was full of praise for his charge afterwards but said he was unlikely to have another run before the Cheltenham Festival.
"Today he had to be a completely different Sprinter," he said. "There was just that concern about coming back to Kempton, but he was really good and Nico gave him a lovely ride.
"They had to be very brave at the last, but he's that sort of horse - he's got the class but sometimes you have to tough it out as well.
"It's all a step forward, but an entirely different step. The other horse looked to be getting the better of it, but the way he's kept on you'd have to say there wasn't a lot wrong."
BBC horse racing correspondent Cornelius Lysaght
When Sprinter Sacre, then carrying all before him, was pulled up in this race in 2013, and a heart condition diagnosed, it was hard to imagine he'd definitely race again let alone win decent-sized pots against big-name rivals.
But the horse who'd had cardiac problems showed heart aplenty to see off Sire De Grugy, whose cause was badly dented by a last-fence jumping blunder.
Sprinter may not be back at his best - Nicky Henderson says he has to improve further to win another Champion Chase - but he's giving great value attempting to get there.