Many Clouds outstayed his rivals to give trainer Oliver Sherwood a second victory in the Hennessy Gold Cup at Newbury.
Sherwood scored with Arctic Call back in 1990 and Many Clouds demonstrated seemingly endless reserves of stamina to triumph under Irishman Leighton Aspell at odds of 8-1.
Houblon Des Obeaux kept on for second as a 50-1 chance, with Merry King third and Monbeg Dude fourth in the Grade Three feature.
Sherwood said: "This is special, it doesn't happen to me
"I'm just chuffed to bits.
"He's a very, very tough horse.
"I'm just delighted for the whole team."
Many Clouds was buried in the pack on the first circuit as What A Warrior, Annacotty and Le Reve set a strong gallop in the early stages.
However, their exertions soon told and they were swallowed up as the challengers were lined up in behind.
Houblon Des Obeaux looked a likely winner as he headed in front of Many Clouds in the straight, with Merry King coming between horses under champion jockey Tony McCoy.
Many Clouds found plenty for Aspell after jumping the last, though, edging ahead on the run-in before eventually pulling three and a quarter lengths clear.
Houblon Des Obeaux hung on for second by a length, with Monbeg Dude staying on with purpose for fourth.
Djakadam, the 5-1 favourite, could be spotted travelling well at one stage but when push came to shove, Willie Mullins' charge had nothing left in the tank and finished out of the frame.
Aspell said: "I used his jumping just to get my position.
"I was very conscious not to be in front too early, this is his first time at the trip.
"It's great to get the opportunity to ride these big winners."