Monbeg Dude benefited from a brilliant Paul Carberry ride to prevent Teaforthree and Tony McCoy giving the home crowd a Welsh-trained winner in the Coral Welsh National at Chepstow.
Dropped out stone last for much of the marathon contest, Carberry began making stealthy headway on the second circuit.
In contrast favourite Teaforthree was up with the pace throughout but looked booked for third turning in as Triggerman and Giles Cross still appeared to be going well.
However, they had been racing from some way out and unfortunately Giles Cross went wrong and was pulled up.
Carberry still head some 10 lengths to find three out but did not panic and joined McCoy at the last and the pair tussled to the line, with Monbeg Dude (10-1) winning by half a length for fledgling trainer Michael Scudamore, who is only based some 40 minutes away from the track.
Triggerman stuck on for third with Arbor Supreme fourth.
Carberry said: "Tom Scudamore said to me I'd love him and to ride him like a non-trier and to just drop him in.
"I took a while to get the keenness out of him then he started jumping well.
"When I pulled him out I knew I had a good chance with four or five fences left. "In fairness I probably got there a bit soon but he kept going to the line, he gave me a great spin.
"It's my second ride for Michael, I got the call on Thursday.
"I haven't had the opportunity to win this so it was about time I took it. This is great. I thought we were going a bit slow but the rest were off the bridle."
Scudamore said: "We only knew on Thursday that Paul was going to ride him as that was when we heard Jamie Moore had to go to Sandown.
"I haven't had the opportunity to win this so it was about time I took it" - Carberry on finally winning the Chepstow highlight
"There was a question of where we would go after he won at Cheltenham, my dad (Peter Scudamore) and all the owners wanted to come here, but I wanted to go back to Cheltenham on New Year's Day as I thought this might be too big an ask for the horse.
"It was an interesting discussion but dad said we were going to the Welsh National, that there was only one place to go and obviously I'm delighted we did."