By Andy Stephens
The heavyweights had been expected to take centre stage in the three-mile feature but Coneygree was pulled up around halfway, having lost his position after setting the early pace, while Cue Card suffered a heavy fall five fences from home when still in contention.
It was the third time in his past ten races that Cue Card has hit the deck and, with his 12th birthday looming, there were calls on social media for the nine-time Grade One winner to be retired.
However, he had not looked out of his comfort zone before his exit and Paddy Brennan suggested afterwards that the triple Betfair Chase winner had been blinded by the sun.
"He couldn't see the fence,” Brennan said. “The further he went the better he travelled but early on he wasn't enjoying the ground."
Trainer Colin Tizzard added: "He's OK, that's the main thing, and so is Paddy (Brennan). He moved upsides just as the real race was starting and he just got it all wrong, which he has done in the past."
The injury-blighted Coneygree, having just his fourth run since winning the 2015 Cheltenham Gold Cup, was instantly sent to the front by Nico de Boinville but stood much too far off the third fence, a ditch, and did well to get to the other side.
After minor errors at the eighth and ninth, he quickly surrendered his lead and was already dropping back when his jockey threw in the towel.
Initial fears that Coneygree might have suffered another injury were dispelled by Sara Bradstock, who offered an alternative excuse for the 7-4 favourite.
"He simply frightened himself at the ditch,” Bradstock said. “He doesn't do that normally and after that Nico said he was just scared.
"He pulled him up because he simply wasn't jumping like he normally does and he wasn't going to win. He is the best jumper in the world normally so something wasn't right. Thankfully he seems fine, he's got a little cut but nothing serious.”
She added: "Nico said the sun was very bright and it might be that he didn't see the fence. We'll go back to the drawing board now and try and get schooling him on the grass. We've only been able to do it on the all-weather up to now."
Bristol De Mai, who started at 6-1, travelled well throughout but the rugged Blaklion, a piunt shorter in the market, got virtually upsides at the final fence. Neither flinched on the run-in, with Bristol De Mai pulling out a bit extra to prevail.
The pair pulled 23 clear of Definitly Red (8-1) in third.
Twiston-Davies said: "Bristol De Mai doesn't turn seven for a few weeks so he should be coming into his own this season, which is amazing given what he has already achieved.
“It will be the Betfair [Chase, Haydock] next for him. He should get his soft ground and he likes it there. He was always travelling and I was just very happy with him.
"Blaklion pleased me, too. He was getting 6lb so the handicapper shouldn't be putting him up. That should leave him spot-on for the Becher Chase (Aintree)."
On winning a record fifth Charlie Hall, the Naunton handler said: "It's the first major race of the season so you can target it a long way out - it's not a prep race."
Bristol De Mai is now a best-priced 5-1 for the Betfair Chase with Boylesports in a market headed by Sizing John at a standout 7-4 with Bet 365. Cue Card, who has won the race three times, is out to a general 8-1, with Coneygree shunted out to 20-1 by Sky Bet.