Barry Geraghty and Kicking King survived a bad mistake at the last fence to take the King George VI Chase at Kempton.
The pair were well ahead coming to the last but the horse stumbled badly on landing but somehow Geraghty managed to hold on.
There was more drama on the run-in as the horse did well to avoid someone dressed as Santa who made a dash across the track in the closing stages.
Although the stumble affected his momentum, Kicking King managed to hold on to the line to give trainer Tom Taaffe a famous victory, 30 years after his father Pat first trained Captain Christy to success in the same race.
"He got very tired going to the last. I went early, probably too early, and I should have waited longer," said a relieved Geraghty after the race.
"He missed a couple on the back straight which I didn't really anticipate because he had jumped so well, and going down to the last he just emptied on me.
"I just grabbed hold of him. I was hanging on to his ears at one stage, but he was good. I gave him a smack and he went again - but then I nearly knocked down Santa Claus!"
Azertyuiop had been Kicking King's closest challenger coming into the home straight but faded in the closing stages, allowing Andrew Thornton and Kingscliff to take second two and a half lengths behind the winner.
It was a brave run by Azertyuiop, who was running over three miles for the first time while Kingscliff's trainer Robert Alner will be encouraged by his charge's run after he missed this year's Cheltenham Gold Cup.
Earlier, the 8-11 favourite Harchibald played a patient waiting game to beat Rooster Booster for the Stan James Christmas Hurdle.
Rooster Booster, ridden by Richard Johnson, made all the running and led by up- to 30 lengths at one stage down the back straight.
But as he tired, the Irish challenger, ridden by Paul Carberry, reduced the gap and took the lead between the last two fences to eventually win by a length and a half and boost his Cheltenham chances.
King George VI Chase, Kempton Park
1. Kicking King (BJ Geraghty) 3-1f
2. Kingscliff (A Thornton) 15-2
3. Azertyuiop (R Walsh) 4-1
13 ran. Dist: 2�, 1�
Christmas Hurdle, Kempton Park
1. Harchibald (P Carberry) 8-11f
2. Rooster Booster (R Johnson) 3-1
3. Perouse (R Walsh) 14-1
7 ran. Dist: 1�, 20