10/3 favourite Al Boum Photo became the first horse since Best Mate in 2003 to win back-to-back renewals of the Magners Cheltenham Gold Cup.
The eight-year-old was providing trainer Willie Mullins with a fourth successive winner at Cheltenham on Friday and led his rivals over the final fence.
Santini (5/1) was switched to the centre of the track by Nico De Boinville to have another crack at the leader up the hill and he began to close in the final 50 yards.
However the market leader had gone beyond recall, scoring by a neck.
Lostintranslation (10/1) was third, just ahead of Monalee (20/1).
Winning jockey Paul Townend said: "It's amazing. I tell you, I'd want some boot in the rear end if I was in front that early and got beat by Santini though. I thought I'd never feel anything like the feeling I had here last year, I think this is even better. It's all about this, it's all about this lad. Unreal, it's a credit to Willie. To come here with one run, the man's a genius."
Mullins said: "It's a fantastic, absolutely unbelievable day. That man there on the screen, Paul Townend, people said he was under pressure. Paul does his own thing, he probably rides better under a little bit of pressure, (it was) really, really good from him.
"(I'm) delighted for Paul, it's not easy to take over from someone like Ruby Walsh, but Paul's gone and stamped his authority this season in Ireland riding for our yard, so I'm really delighted for him."
On having the same preparation as last year, he said: "We just decided to follow what happened last year, why change it if it works? Thankfully it paid off. I think it was only history against him today. I didn't think the race was as tough as last year, Paul was brave on him and the whole thing came together. It's Paul's day today."
Nicky Henderson said of the gallant Santini: "You have got to be very proud of him and pleased for everybody, it was a great run. You couldn't have done anything else. He never touched a fence, he was in the perfect position the whole way.
"He fought like a lion. There was nothing else you could do. The winner was better by a neck on the day. To be fair this is only his sixth steeplechase and he has only got to improve a neck and (another 100 yards) and he was nearly going to get there. After what Champ did (in the RSA), I couldn't hope for that twice. He was a couple of lengths down at the last and has got back to within a neck. Nico (de Boinville) gave him a beautiful ride. It was a very good race.
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"There is a very big difference between first and second, but Willie is a great mate and Joe (Donnelly, owner) has got a couple of lovely young horses with us, so I'm thrilled for them, as they great people.
"This will be the only objective next season and I've told Willie he isn't allowed any prep race, not even in January! Somebody has to finish second - it is a hard place to be, but we can't complain."
Colin Tizzard was also proud of the effort of Lostintranslation.
He said: "It was a brilliant run in the end. We've had a hard old week, as nothing has been going right and we have had a few dirty noses at home and we thought, 'should be running this one', as that is how bad it got today. Then he come and runs like that, with the choke out a bit. He had every chance. He was just beaten by two better horses. It was a fantastic run."
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