Kauto Star just held on from Imperial Commander in a pulsating renewal of the Betfair Chase at Haydock.
The pair had it between them all the way up the straight, with a fine leap three out from Kauto Star looking to have given him the advantage.
But Imperial Commander - unproven over the three-mile trip - really dug deep and was getting back at the 4-6 favourite all the way to the line.
A tense wait ensued as the judge studied the photograph, with the verdict going to Kauto Star by a nose.
Delighted winning trainer Paul Nicholls said: 'I have had more sleepless nights than ever this week as the horses have just taken a while - Ruby (Walsh) just said he needed it which is what I wanted to hear.
'I couldn't go to Kempton (King George) without a run as it's a long time to go without a race and to hear him say that is just what I wanted.
'I thought he might just get a little bit tired. He keeps finding and he's a real professional. Of the three races (he is scheduled to run in this year), this is the least favoured - Kempton and Cheltenham (Gold Cup) are what he wants.'
Walsh added: 'He's always digs this horse - he's an incredible horse.'
