The scene where Annie Power and Ruby Walsh come to grief as well as L'Unique and Wayne Hutchinson© Photo Healy Racing
Annie Power fell at the final flight when in front to leave stablemate Glens Melody to land the OLBG Mares' Hurdle.
Bookmakers were left breathing a sigh of relief after the heavily-backed odds-on favourite came to the last clear of her rivals but took off too soon, hit the obstacle hard and crumpled to the ground, leaving the race wide-open.
Happily both Ruby Walsh and Annie Power were quickly on their feet, as Glens Melody - second to another brilliant Willie Mullins mare, Quevega, in the same race 12 months ago - took over the lead. Polly Peachum and Barry Geraghty emerged from out of the pack to give chase up the run-in and it was tight at the line but Glens Melody (6/1) prevailed by a head from Polly Peachum (9/1), with the gutsy Bitofapuzzle (16/1), who was handy from the start, staying on again for third only a neck further back.
There was an unusually muted response from the Cheltenham crowd as the winner and jockey Paul Townend returned to the winner's enclosure - many of the crowd would have been clutching tickets involving the four Mullins 'bankers', the first three of whom had already won and of which Annie Power was the last to run.
Townend said: "It's not the nicest way to win, but she deserves it as she's a great mare. "(I'm pleased) for the owners who kept her in training and gave me the ride. I'm delighted. It's brilliant."
Mullins added: "Annie is up all right and Ruby is up all right, so everyone is fine and we can enjoy Glens Melody now.
"I thought Annie just stood off - she was probably going too well.
"I'm delighted for Fiona (McStay, owner) who was right to keep her in training and come back for this race.
"Paul is a fantastic guy. It's great he's had a winner on the first day of Cheltenham. You couldn't write a script like today.
"Last year she was robbed by Quevega having jumped the last in front and this year she got the rub of the green."
Although it may not have been achieved with the horse many had expected, Mullins was still in the winner's enclosure for an amazing fourth time on the day. "It's unbelievable to have four winners in one day," he added.
"I keep thinking this is not real and it won't last forever, so I'm going to enjoy it now."
Despite the fall, Ruby Walsh was still able to reflect upon "a super day".
"I thought she'd gallop her way through it, but instead she went to have a go at the last, hit the top bar and that's what happens. She's fine, it's one of those things," he said.
"It's been a super day. Douvan was great, Un De Sceaux was brilliant, Faugheen winning the Champion Hurdle was magic. At least Annie Power got up and there'll be another day."
Nicky Henderson said of Polly Peachum, another placed runner for Seven Barrows after Josses Hill in the Arkle: "We're getting close. There isn't a mares' race for her at Aintree and if we go to Punchestown we will bump into Annie Power again."