Kauto Star put his supporters through the mill as Imperial Commander made him pull out all the stops to register a 12th Grade One success in the Betfair Chase at Haydock.

The dual Cheltenham Gold Cup winner was all the rage to land the prize for a third time but only did so by the narrowest of margins after a tense wait for the judge to split the pair in a nail-biting finish.

Paul Nicholls' champion had a fight on his hands when unshipping Sam Thomas at the final fence 12 months ago and was again pressurised under Ruby Walsh jumping the same obstacle alongside Imperial Commander.

The 4-6 favourite held a narrow advantage on the run-in but was pressed right to the line by the Ryanair Chase winner and just a nose separated them after a gruelling three-mile slog in testing conditions.

Any suggestions of a below-par effort were swept aside by the 24-length margin back to last year's Hennessy winner Madison Du Berlais in third, while Irish raider Notre Pere dropped tamely back to fifth.

A relieved Nicholls punched the air as Kauto was called the winner, and he said: "The best three words I have heard Ruby say are 'he needed it'.

"This week has been one of the most nerve-wracking I have ever had as I was slightly nervous of the ground and some of the horses have been slow to come to hand.

"I couldn't go to a King George without having a run and the ground wasn't the issue as much as him getting a bit tired in it.

"That run will sharpen him enormously and put him right for Kempton.

"He hadn't run since March, so jumping 18 fences in a race will bring him on mentally and physically.

"Nigel's (Twiston-Davies) horses all run well first time out and I feared Imperial Commander coming here fresh.

"We did want to win today, but it is a bigger picture and I have learnt that you can't have them at their best for their first run of the season - you need to leave enough improvement.

"We can just fine tune him now for the King George and then go to Cheltenham so I am absolutely delighted.

"To see him stick his head down and fight at his age is absolutely fantastic and is what racing is all about.

"That was a great spectacle compared to him winning with his head in his chest. They were two great horses in a great race and to win is fantastic."

An elated Walsh said: "I did think we were beaten and the second is an improving horse.

"He feels as good as last year, he's a wonderful horse.

"That is his 12th Grade One and people were still knocking him last week. It is a bit like Manchester United - if you are at the top they want to knock you.

"This is as good a horse as we have ever seen and we should all appreciate him."

Owner Clive Smith was another to think he was beaten.

He said: "I was standing next to Charlie Mann and he said we had won, but I wasn't so sure.

"I still don't know how he won watching the replays again but Ruby did say he would come on a lot for the run."

Kauto Star will now try for an unprecedented fourth consecutive win in the William Hill King George VI at Kempton on Boxing Day and the sponsors left him unchanged at the head of the market at 10-11 and trimmed the runner-up to 5-1 from 12s.

Gold Cup sponsors totesport leave Kauto Star unchanged as the 6-4 market leader for a third blue riband and clipped Imperial Commander into 10-1 from 20s.

Twiston-Davies said: "From every angle I saw he had got it, but there you are. I am sure the camera doesn't lie and he has run a hell of a race.

"We have to think whether we go back to the King George as he obviously prefers going left-handed. There aren't many options so we will probably have to go there.

"If this had been three miles and two furlongs then he would have won easily - bring on the Gold Cup."

Walsh National winner Notre Pere had been fancied to bustle up Kauto Star but the soft-ground lover failed to fire.

His rider Andrew Lynch said: "It is disappointing, he never really travelled and we weren't going that quick.

"I'd say he was feeling something and we will have to check him out when we get home."