Annacotty lifted the Paddy Power Gold Cup at Cheltenham for trainer Alan King and jockey Ian Popham.
Having his first run for King's Barbury Castle yard, it was a deserved success for Popham, who has seen his career blighted by injury.
Irish Cavalier looked to have everything covered at the third-last, which he jumped together with Double Ross and favourite Kings Palace, who had assumed control before four out when moving smoothly to the head of affairs.
But as is often the case at Cheltenham, it was a much changed picture from the last, with Annacotty (12-1) staying on strongly to repel the late thrust of Buywise by half a length.
Sound Investment was another three-parts of a length back in third, with Double Ross fourth. Remarkably, Irish Cavalier finished out of the frame.
Popham said: "I just want to say a big thank you to the owners and their racing manager, and to Mr King for letting me keep the association with the horse, it means a lot to me.
"I was just hoping for a bit of rain this morning because he stays very well. I knew his stamina would come into play, he jumped brilliantly and travelled everywhere I wanted to.
"He dug deep at the end for me and it's a great training performance to win first time up without a run."
Popham won the Grade One Kauto Star Novices' Chase with Annacotty at Kempton on Boxing Day of 2013, and was recording his fifth win on the seven-year-old, who was formerly trained by Martin Keighley.
He added: "I'm delighted for the horse, he's been very good to me. That was the most incredible feeling, I honestly thought my career was on its backside at start of season, I was really struggling, riding some moderate horses and it was getting to me.
"That's only my third win of the season and until last week I hadn't had a winner at all. It just shows how this game goes. I'll have to pinch myself, it doesn't feel real."
Popham won the Grade One Kauto Star Novices' Chase with Annacotty at Kempton on Boxing Day of 2013, and was recording his fifth win on the seven-year-old, who was formerly trained by Martin Keighley.
He added: "I'm delighted for the horse, he's been very good to me. That was the most incredible feeling, I honestly thought my career was on its backside at start of season, I was really struggling, riding some moderate horses and it was getting to me.
"That's only my third win of the season and until last week I hadn't had a winner at all. It just shows how this game goes. I'll have to pinch myself, it doesn't feel real."
