Jessica Harrington struggled to comprehend the magnitude of her achievement after Sizing John ran out a brilliant winner of the Timico Cheltenham Gold Cup.
The County Kildare-based trainer is no stranger to success at Prestbury Park, most notably landing two Queen Mother Champion Chases with the great Moscow Flyer and the Champion Hurdle with Jezki.
However, she had never even saddled a runner in the blue riband before going for gold with Sizing John - who was formerly trained by Henry de Bromhead - and opened her account at the first attempt.
"I can't believe it, it was amazing how he jumped and travelled," said a shell-shocked Harrington.
"I've never had a runner in the race before so to train the winner - I don't know when I'll come down to earth. I feel like I'm about to wake up and it hasn't happened.
"This is the jewel in the crown, I've been watching and listening for as long as I can remember.
"I feel a bit sorry for Henry de Bromhead as I only inherited him in September and I had to get to know him and how to train him.
"He's only seven so I've got to keep him right and mind him. I've no idea what he'll do next, all I was thinking about was this race."
Placed behind the mighty Douvan on no less than seven occasions, the seven-year-old confirmed himself a major contender with victory in last month's Irish Gold Cup at Leopardstown.
Some suspected another two furlongs and the famous hill would prove a step too far, but having travelled powerfully in the hands of Robbie Power, 7-1 shot Sizing John moved to the front rounding the home turn and galloped all the way to the line for a two-and-three-quarter-length triumph.
"He was running over two miles and if Douvan hadn't been around, he would probably have stayed over that trip," added Harrington, who for good measure also took the Grand Annual, the concluding event of the four days, with the Power-ridden Rock The World.
"He was almost forced to step up to two and a half and three miles and I genuinely thought, with him being only seven, that he should go for the Ryanair Chase. But Alan Potts (owner) wanted to go for the Gold Cup, it was Robert who said he would stay, and he did.
"I was thinking it was all going a bit too easy. I was glad that on the first circuit he put a few short ones in and he wasn't winging fences. When he pulled him out on the second circuit, he began jumping well. Just at the top of the hill I saw Robert give him a squeeze and he flew."
Potts was left fighting back the tears, and said: "It's unreal, it's my dream and it's come true. It's our first runner in the race, the jockey's first ride and Jessie's first runner."
Power, who won the Grand National on the Gordon Elliott-trained Silver Birch in 2007, said: "Unbelievable, Jessica Harrington is a genius. I always said when this horse stepped up in trip he'd win.
"I was only 25 when I won the National and I'm 35 now. When you're 25 you think you can win everything, so this is very special."
Minella Rocco flew home to fill the runner-up spot and his trainer Jonjo O'Neill said: "It was his first run proper of the season, he has no miles on the clock and he'll improve a ton on that.
"I'm thrilled, he had a great spin round and finished as strongly as anything. He will definitely run again this season, but first let's get him home and see how he is."
Colin Tizzard's Native River was a close third, just ahead of Djakadam, who had finished runner-up in the last two renewals.
Owner Garth Broom said of Native River: "I felt we were slightly robbed of second right on the line, but finishing third in a Gold Cup with a seven-year-old is something you can't complain about.
"He wears his heart on his sleeve and we are so proud of him. He may go to Aintree for the Bowl as he ran well there last year, depending on how he comes out of his race."
Djakadam's trainer Willie Mullins said: "I'm disappointed he only finished fourth, but he was a bit unlucky with that jump at the second-last, before which he had jumped perfectly. We might think of something else next year because I'm asking myself 'did he really stay?'."
Cue Card, who blew a possible £1million bonus when falling at the third-last in 2016, came down at the same fence again, but was reported none the worse.
Lizzie Kelly, the first woman to ride in the race in over 30 years, only got as far as the second fence before parting company with Tea For Two.