Gold Cup hero Denman suffered a shock defeat on his return from a 330-day absence at Kempton.
Off the track since his Festival heroics, the Paul Nicholls-trained nine-year-old jumped sketchily in the early stages of the Levy Board Chase - but all looked well when he went to the front before the seventh-last.
But David Pipe's Madison Du Berlais (12) was always going well upsides and the writing was on the wall three from home.
Tom Scudamore's mount quickly opened up a healthy gap and came home in splendid isolation, with runner-up Denman 23 lengths in arrears.
Connections have always felt Denman is a much better horse going left-handed, and this display did nothing to disprove that theory as he lost his unbeaten record over fences.
Victor Chandler were quick to react by making Kauto Star 2-1 favourite (from 11-4) for the Gold Cup, with Denman out to 11-4 from 7-4.
Hennessy winner Madison Du Berlais is clearly on an upward curve and was slashed to 8-1 from 66s for top honours at Cheltenham in March.
King George runner-up Albertas run was a major disappointment and never looked happy under Tony McCoy as they trailed home a long way back in third.
A downbeat Ruby Walsh said: ‘I'd be lying if I said I wasn't disappointed. I thought it would be a matter of just turning up.
‘In fairness to David Pipe and Tom Scudamore, they knew they were up against a horse that hadn't run for a long time and they turned it into a slog.
‘It took me a bit to get him involved and to get him on an even keel.
‘But I got him interested down the back and he travelled great.
‘But Tom upped it a gear and had me struggling.
‘He was fairly tired (at the finish), but we consolidated our position without tiring him into the ground.’
Pipe, by contrast, waxed lyrical about the performance of Madison Du Berlais.
‘He's been a great horse for the stable and for the owners over the years - he's still improving,’ said the Pond House handler.
‘The sheepskin side-pieces have helped him as much as Tom, because he always hit a flat spot in his races.
‘He gets further these days and is clearly in great form - it was an unbelievable performance.
‘I'm sure we haven't seen the best Denman, but you can't take anything away from our fellow.
‘I'm sure we were fitter than Denman and we are also probably better on a flatter track.
‘The Gold Cup's another day - maybe this was our Gold Cup - but he definitely deserves his chance (at Cheltenham).
