Golden Ace was a shock 25-1 winner of the Champion Hurdle at Cheltenham after previous victors Constitution Hill and State Man fell.
The 2023 champion Constitution Hill was sent off odds-on favourite but came down early in the big race.
Last year's winner State Man looked set to claim victory before a dramatic fall at the last hurdle.
That left Golden Ace, ridden by Lorcan Williams for trainer Jeremy Scott, to come through and win by nine lengths from 66-1 outsider Burdett Road.
Lossiemouth retained her Mares' Hurdle crown in convincing style, and left many wondering how she might have fared in the Champion Hurdle.
The Willie Mullins-trained grey, owned by Rich Ricci, was handed the easier challenge after falling in the Irish Champion Hurdle last time out.
And the 4-6 favourite cruised to victory under Paul Townend by seven and a half lengths from stablemate Jade De Grugy for a third triumph at the Festival.
"She was very good. I was disappointed with the fact she didn't run in the Champion Hurdle, but her work with State Man last week wasn't Champion Hurdle work so the obvious thing was to come back," said Mullins.
"It's disappointing for everyone but you look at where you can get winners. Rich hasn't got a big team of runners so we have done the right thing for Rich."
The meeting got off to the perfect start for favourite backers as Kopek Des Bordes also justified odds of 4-6 for Townend and Mullins, a victory greeted by hearty cries of 'Ole, Ole, Ole' from the stands.
It was an emotional success for owner Charlie McCarthy, who was diagnosed with kidney cancer at the start of this year and had surgery last month.
"I'm on cloud nine. I just can't get over it. I'm walking on air," said McCarthy.
There was a poignant runner-up in William Munny, running in the same yellow and blue silks of trainer-owner Barry Connell, who triumphed with Marine Nationale two years ago.
The contest was renamed the Michael O'Sullivan Supreme Novices' Hurdle in honour of the Irish jockey who won on Marine Nationale. The rider died last month aged 24 after a fall.
Mullins hoped to follow up his opening win in the Arkle Chase but a blunder at the penultimate fence from Majborough cost him the race.
Both L'Eau Du Sud and Only By Night looked like potential winners before Henderson's 5-1 chance Jango Baie stormed through with a late run under Nico de Boinville to snatch victory.
The winner had traded at odds of 300-1 in-running and his victory saved bookmakers who were fearing payouts into the millions if all four hot favourites won on Tuesday.
Scottish trainer Lucinda Russell won the Ultima Handicap Chase for the third time in four years as Patrick Wadge guided Myretown to an 11-length demolition with an exhibition round of jumping.