Kauto Star could not return to winning ways as Aintree's Grand National Festival began in exciting fashion.
The eight-year-old, a well-beaten favourite in the Cheltenham Gold Cup, started at 4-7 for the Totesport Bowl.
But he produced a number of jumping errors and was beaten by a nose by Our Vic (9-1) despite leading at the last.
Earlier, triple Cheltenham champion Inglis Drever was beaten into third place as Blazing Bailey won the Liverpool Hurdle by six lengths.
"Ruby's not happy with me. I told him to be positive with him, probably he should have just got a lead and not have been so positive"
Our Vic and Kauto Star took each other on early in the second race of the meeting and two of their three rivals, Gungadu and Monet's Garden, were in trouble with a circuit to run.
Kauto Star's first error led jockey Ruby Walsh to take up the running for a couple of strides before the Gold Cup runner-up came back on the bridle.
Exotic Dancer tracked them into the straight but he was soon left behind as a flying jump propelled Kauto Star into what seemed an unassailable lead three out.
However, he then made a mistake characteristic of his earlier chasing victories, taking off too soon and putting his front legs through the birch at the second-last.
Kauto Star did not appear to lose too much momentum but his stride was patently shortening before the last and Our Vic was running on stoutly for Timmy Murphy.
A final thrust saw the David Pipe-trained horse, a gutsy winner of the Ryanair Chase at Cheltenham, narrowly pip Kauto Star on the line.
606: DEBATE
Pipe said: "Our Vic and Timmy have given their all. He's battled back, he's got a good jump at the last.
"Blinkers have definitely helped him and sharpened him jump.
"He's a very good horse and has been a good horse all his life. Whenever this fellow retires we'll miss him."
Kauto Star's trainer Paul Nicholls said: "Ruby's not happy with me. I told him to be positive with him, bowl along - probably he should have just got a lead and not have been so positive.
"We get it right more times than we get it wrong. I'll take the blame."
Inglis Drever's trainer Howard Johnson said after his horse's race that the three-time World Hurdle champion would only have three more races in his career.
After seeing the 13-8 favourite finish third behind Blazing Bailey (5-1) and Faasel (20-1), Johnson said: "If he'd pinged the last he would have been closer, but this is not his track.
"We'll put him out for the summer now and see how he is.
"If he runs again next season the plan will be the same as this year - Newbury, the Cleeve Hurdle and then the World Hurdle."
VC Bet make Blazing Bailey 6-1 for next year's World Hurdle at Cheltenham, the race Inglis Drever has won three times.
It was a bad day for Cheltenham heroes all round, as this year's Triumph Hurdle winner Celestial Halo was beaten by Tony McCoy and Binocular in the Novices' Hurdle.
Binocular, trained by Nicky Henderson and owned by JP McManus, justified his 11-8 favourite's tag, beating Celestial Halo by seven lengths.
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