Significant market driver Shishkin edged out Abacadabras to win a thrilling Sky Bet Supreme Novices' Hurdle.
Ante-post favourite over the last three weeks, Nicky Henderson's charge was friendless in the market and sent-off at 6/1.
In contrast, the runner-up was the market springer on Tuesday and as he went to the front approaching the last, his supporters looked set to collect.
However Nico De Boinville was producing the winner with a telling challenge too and the pair duelled up the famous hill with only a head separating them at the line.
Asterion Forlonge set out to make all the running but jumped badly to his right, including at the second last when he cannoned into Elixir D'Ainay, bringing him down.
The winning jockey told ITV Racing: "It wasn't a very nice experience if I'm being honest with you, everything that could go wrong did go wrong. But it just shows what a good horse he is and I can't wait for him to go chasing next season. I pulled him out at the top of the hill to get a bit of daylight and then he picked up again. This is was a big relief and great to get on the board, especially after the disappointment of Altior tomorrow. It's great to get one on the board and great for the team."
Henderson - who has been forced to rule stable star Altior out of the Champion Chase - said: "We say it every year, that something will come and bite you and sadly this year it was Altior, so it's a relief to begin with a winner.
"He was one of our more powerful shots of the week, but all three ran well really (Allart was fifth) - they are three lovely horses.
"I couldn't see what was happening to Shishkin coming down the hill, he got slightly hampered and Barry (Geraghty) looked in the right place on Chantry House, but Shishkin has got those gears - and he needed them. Nico was cool-headed, we know he's cool round here."
He added: "Both Shishkin and Chantry House are chasers of the future - both gorgeous horses for the future so we've a lot to look forward to. As former point-to-pointers I'd imagine they'll go chasing, but we'll see."
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