Crambo secured back-to-back Grade One Long Walk Hurdle victories by beating Hiddenvalley Lake in wet conditions at Ascot.
The seven-year-old, trained by Fergal O'Brien and ridden by Jonathan Burke, passed leader Beauport in the closing stages before holding off a late attack by Hiddenvalley Lake to defend his crown.
"I'm speechless," O'Brien told ITV4. "I'm so grateful for everyone at home. It's not been easy. I've had bad days."
Beauport finished in third with The Wallpark in fourth place.
Since winning at Ascot 12 months ago, Crambo has struggled to recreate the same form, having disappointed at Cheltenham and Aintree in the spring.
Setting off at 9-1, Crambo needed plenty of stamina to overtake Beauport, who started strongly and looked to be heading towards a comfortable victory before a heavy jump at the final fence gave the other front-runners a chance to catch up.
Strong Leader, who was the favourite, finished 10th and never looked a threat for the win.