Paul Nicholls had to wait until the penultimate race of the Festival to taste victory as Salubrious (16/1) took the Martin Pipe Conditional Jockeys' Handicap Hurdle.
The maestro of Ditcheat had had a Festival to forget but he finally got himself on the board as the six-year-old stayed on from way off the pace to land the spoils.
Double Ross and Stopped Out attempted to set the pace and both had every chance as the race began in earnest with two flights to negotiate.
Nigel Twiston-Davies' charge fared best of that pair and kept on determinedly but he could not repel the winner as he flew past him, and having given his all, he eventually completed the race in third.
Nagpur stayed on to be a never-nearer second, with Make Your Mark back in fourth.
Gevrey Chambertin was the subject of a substantial gamble, though the bookmakers were never in with too many doubts as he was hard at work from a relatively early stage.
Nicholls said: "It's been a blooming nightmare this week but I'd like to dedicate that one to Dominic Baker (son of Nicholls' head lad Clifford Baker, who died in a car accident recently).
"It's been an incredibly tough week, but to win for Dominic is brilliant. For Harry to ride it is brilliant.
"He gave it a peach, I told him to go as wide as he could but not to get there too soon but he was probably there 10 minutes too soon! Harry rides very well and if he gets some more experience he'll be great.
"He had a chance on his At Fishers Cross form but we thought the ground would be too soft and the way this week has gone I thought he'd get caught."
Derham said: "It's been a tough week and it's so competitive here at the Festival, our horses had run well without winning, this is incredible.
"We thought we'd ride him to come through horses and he made my life very easy because he can be a bit keen. He jumped great and travelled well and I've got there too early really."