He lodged one of only two triple clear rounds of the competition.

Fifty of the world’s best riders line out in Longines Grand Prix and the young Wexford rider, who turns 19 this August, was flawless throughout the class with the 10-year-old mare Molly Malone V.

Allen and Ballywalter Farms' mare finished one-third of a second faster than their nearest challenger, 44 year-old Dutch Olympic team medallist Jur Vrieling and Flash Dance vd Kalevallei.

Speaking to The Irish Field as he travelled to his next two-star show in Redefin, Germany, this weekend, Allen said he was delighted with the mare’s performance, only her third Grand Prix of that level.

“She did a lot last year, coming along behind Romanov but I only really stepped her up a level in the last six weeks,” he said.

Commenting on the young rider’s performance, Irish show jumping manager Robert Splaine said: “It was a tremendous achievement. I don’t think anyone that young has ever won a five-star Grand Prix, maybe Rodrigo [Pessoa], but a lot of really good riders go their whole lives without winning a five-star Grand Prix and here is Bertram after winning at 18. He’s just a winner.

“Bertram also contributed as a team member towards Ireland's joint third place in the Lummen Nations Cup on Friday, and it's worth noting that all four members of that team have now had individual wins at Lummen.

Bertram polished off what has been a fantastic week for Irish show jumping here,” added Splaine.

Allen and Molly Malone had four faults in the first Nations Cup round and went clear in the second round, helping Ireland to finish equal third.

See page A52 for the full report.