Politologue got the better of hot favourite Min in a thrilling climax to the JLT Melling Chase at Aintree.
The two-and-a-half-mile Grade One was billed as a match between the Willie Mullins-trained Min, who chased home Altior in the Queen Mother Champion Chase at Cheltenham, and fellow Irish challenger Balko Des Flos, who was an impressive winner of the Ryanair Chase at Prestbury Park for Henry de Bromhead.
However, the Paul Nicholls-trained 11-1 shot Politologue, who was only fourth in the Champion Chase, did not read the script and claimed a narrow victory under Sam Twiston-Davies in a race in which owner John Hales lost the hugely popular grey One Man 20 years ago.
Twiston-Davies said: "It was a good shout by Paul to put the hood back on, it helped him relax and he got in a great rhythm.
"Paul has done all the hard work and I just pushed at the end.
"When Min came up all I was hoping was that I winged the last to have a chance again, when something is travelling like that you are always concerned but one thing with him is that he tries very hard."
He added: "I needed that one, it's been a trying time, Paul is trying to rebuild, looking for new stars, I've been injured, I got a few decisions wrong, missed a few winners and gave some horses some not-so-great rides, but these ones make it worthwhile and help me to believe in myself again."
Balko Des Flos took the six-strong field along for much of the way, but he was a spent force early in the home straight and it turned into a straight match between Min under Paul Townend and Politologue.
Min looked to be travelling marginally the better of the pair between the final two fences, but Politologue, wearing a hood for the first time this season and fitted with a tongue-tie for the first time in his career, refused to bend and got the better of a pulsating dual by a neck.
Politologue won the Haldon Gold Cup, the Tingle Creek and the Desert Orchid Chase earlier in the campaign before proving no match for the brilliant Altior in the Game Spirit at Newbury or at Cheltenham.
The seven-year-old looked likely to win the Maghull Novices' Chase at last year's Grand National meeting when stumbling and falling after the final fence.