Medermit took advantage of the final-fence exit of Captain Chris to win the Betfred Haldon Gold Cup Chase at Exeter.
Captain Chris rallied to challenge Medermit and Cornas at the last, but he blundered badly and Richard Johnson was unseated.
That left Medermit (7-2) to pull away from Cornas to score by a length and a quarter.
Oiseau De Nuit was two and a quarter lengths back in third and the disappointing Ghizao only fourth.
Robert Thornton decided to kick on some way out on the grey and despite Cornas travelling sweeter, Medermit kept on finding.
King told At The Races: "Mine have tended to want a run a little bit, but we've got plenty of work into this lad in the last week to 10 days.
"It looked a logical starting point. But I've no idea where I'm going to go with him now.
"We'll enjoy today first and go home and think about it.
"I think Captain Chris might have won, I've only seen it once, but it's bad luck on them.
"I'm sure he wants further. He's in the Paddy Power, but I think that's going to come too quick.
"I only popped him in here because we were worried that if the rain hadn't arrived we couldn't have run today.
"The Peterborough Chase would be a logical step but whether there would be something in between I don't know.
"I think I got it wrong last year dropping him back to two miles. Choc (Thornton) said it took him a few fences to find his stride today.
"I think two and a quarter miles at Exeter, first race (of the season) was the right place, win or lose. We'll definitely go two and a half mile plus from now on."
