Unioniste eventually wore down admirable veteran Neptune Equester to claim the Ivan Straker Memorial Chase at Kelso.
The Paul Nicholls-trained eight-year-old disappointed on his first couple of starts of the season, but fared better when third in a handicap chase at Sandown a fortnight ago.
Nick Scholfield's mount was a 10-11 favourite to beat three rivals in this three-and-a-quarter-mile conditions event and was always travelling smoothly towards the front end.
The grey was passed heading down the back straight as Derek Fox committed for home aboard the teenage Neptune Equester.
Scholfield did not panic, though, and Unioniste regained the lead as the pair bypassed the dolled off second-last before galloping nine lengths clear.
Paddy Power cut Unioniste to 25-1 from 33-1 for the Grand National at Aintree, a race in which he only made it as far as the fifth fence last April.
Owner John Hales claimed the world's most famous steeplechase with Neptune Collonges in 2012.
Scholfield told Racing UK: "At the start there was a few wanting to make the running and I think Soll was a bit deliberate over the first couple. We jumped our way to the front, travelled away nicely and jumped relatively well.
"I was keen coming down to the last not to be in front for too long as I remember Ruby (Walsh) riding him one day at Newbury and he got to the front and pricked his ears. With the second-last being out, it would have been a long way for him, but he stuck at it well.
"He had a heavy fall in the Grand National last year and on his first couple of runs this year it just took him a while to get his confidence back.
"The last run was a very good run at Sandown and was a step in the right direction, and today will have done his confidence no end of good, so it's very pleasing."
Asked about his Aintree chance, Scholfield said: "He's certainly coming to himself now and he'd love the ground and love the distance (of the National).
"If he could get a clear round, he has the right sort of weight.
"He has a lot of things going for him."
