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 Gold Cup before winning it with Sizing John, whom she had started training only in September.

"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.

Placed behind the mighty Douvan on no fewer 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.

"I genuinely thought, with him being only seven, that he should go for the Ryanair Chase.

"But owner Alan Potts wanted to go for the Gold Cup, it was Robert who said he would stay, and he did."

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 for Gloucestershire trainer Jonjo O'Neill.

Colin Tizzard's brave Native River outstayed Djakadam for third.

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.