The Cheltenham Festival is regarded as the pinnacle of jumps racing - the place where winners are more keenly desired than anywhere else.
With all the top talent in Britain and Ireland converging on the Cotswolds for four days in March, it makes for thrilling equine entertainment.
Inevitably, that entertainment-factor is driven by the promise of unpredictable results. Whether they are big-priced winners or shock defeats for short-price favourites, Cheltenham in March has a storied history for producing the scarcely believable.
Here we recall some of the biggest upsets down through the years.
1990 Gold Cup
The centrepiece of the Cheltenham Festival is of course the Gold Cup, the crème de la crème of the staying chasers from Britain and Ireland coming face-to-face for the most prestigious prize in National Hunt racing.
With such an array of talent on display year on year, rank outsiders winning isn't the norm but that was the case in 1990.
The unfancied 100/1 chance Norton's Coin scored in the hands of Graham McCourt, with victory made all the more extraordinary by the fact he was owned and trained by Sirrell Griffiths, a dairy farmer from Wales who had only two other horses in his stable.
The defending champion Desert Orchid was odds-on favourite, but could manage only third as Toby Tobias was within a length of Norton's Coin at the line.
He became only the second winner to be trained in Wales - the first was Patron Saint in 1928 - and his trainer revealed he had only been entered due to a mistake over the deadline for another intended target!
2015 Mares' Hurdle
It doesn't have to be a rank outsider or a long odds-on favourite being beaten to cause a Cheltenham upset of epic proportions - sometimes fate conspires to provide one.
That's what happened in the 2015 Mares' Hurdle, when hot favourite Annie Power was seemingly carrying the hopes of every punter in the land.
Record-breakers Willie Mullins and Ruby Walsh - the all-time winning-most trainer and jockey at the Cheltenham Festival - had enjoyed a scintillating start to the meeting after Douvan won the Supreme, Un De Sceaux landed the Arkle and Faugheen obliged favourite-backers in the Champion Hurdle.
The mood in Cheltenham and much further afield suggested that many had accumulators running up on a Mullins/Walsh four-timer and they must have felt that the hardest part was over by the time Annie Power went off as 1/2fav in the Mares' Hurdle.
Walsh sent the strong-travelling mare into the lead jumping the second last and she quickened clear on the run to the final flight, lots of daylight between herself and the pack.
Annie Power took off a stride too soon at the final flight, clipped the top and sprawled down on the landing side, with Walsh adamant she'd jumped the shadow of the obstacle in front of her.
The gasp from the packet stands was as audible as the cheers that greeted Mullins and Walsh's domination through the early afternoon. It remains one of the most seismic defeats punters have suffered.
2019 Albert Bartlett Novices' Hurdle
Rachael Blackmore has gone on to rewrite the history books but in 2019 she was still something of an unknown at this meeting.
Her first winner came on A Plus Tard in a novices' handicap chase as they blitzed the field in devastating fashion, while her second was on 50/1 Minella Indo two days later in the Albert Bartlett Novices' Hurdle - her first Grade 1 winner at Cheltenham.
Remarkably, Minella Indo would go on to win the 2021 Gold Cup, with Blackmore and A Plus Tard behind in second, while 12 months later, the Festival's most successful female rider of all time would reverse those placings when she became the first lady to ride the Gold Cup winner.
Hard to believe, given what has happened since, that Henry De Bromhead's Minella Indo was a 50/1 chance as a novice hurdler. That he was, but he made a mockery of those odds under a sublime Blackmore steer leaving favourite Commander Of Fleet to settle for second in front of Allaho with future 50/1 Stayers' Hurdle winner Lisnagar Oscar in fifth.
1989 Champion Hurdle
There have been just two 50/1 winners of the Champion Hurdle since it was first run in 1927, Kirriemuir for the great trainer Fulke Walwyn in 1965 and Beech Road in 1989 – they remain the joint-biggest SPs in the history of the two-mile Championship.
The Toby Balding-trained seven-year-old defied those odds but, had it not been for a telephone call between Balding and owner Tony Geake just days before his triumph, then Festival glory may never have materialised, recalled his jockey Richard Guest years later when telling of the original plan to carry top-weight in a Sandown handicap the week before Cheltenham.
He was, felt Guest, a much better horse around Cheltenham and so it came to pass as he won, with 1988 winner Celtic Shot in third, ahead of the favourite Celtic Chief, who had been third a year before but would never manage to complete his set of podium finishes.
2023 Stayers' Hurdle
Sire Du Berlais won the Pertemps Final at this meeting in 2019 and 2020 for Gordon Elliott but he was a 33/1 afterthought to most ahead of the Stayers' Hurdle in 2023.
He'd tried the day three feature in 2021 and finished second to Flooring Porter, before having another tilt the Pertemps (11th) a year later.
His form heading to Cheltenham 2023 was just patchy, defeats in Ireland behind the likes of Home By The Lee, Blazing Khal and his Elliott-trained stablemate Teahupoo suggesting he'd have a bit part role to play at best in the Grade 1 showdown.
As it turned out, Mark Walsh's partner came up the hill strongly, getting the best of Teahupoo and the desperately unlucky Dashel Drasher in a thrilling battle.
He was the second-biggest priced winner of this race since the turn of the century and left a strong field stunned behind him. Teahupoo is a 12/1 chance to go a place better in 2024.