In a slogging finish to the feature, Barclay delivered a brilliantly-timed run to clinch victory with the pacer trained by his partner, Lauren Pearson.
Duke Of Wellington notched Pearson’s biggest training win and first group race victory in 21 years of training a small but select team.
The trainer could only recall Montecrengle in the 2010 Supremacy Stakes Final as her previous group race entrant.
"Its a really big thrill. I think Montegrengle is the only one I have had run in a big race," Pearson said.
Duke Of Wellington gave Pearson her biggest training thrill in what is expected to be his last start for her stable.
The pacer was purchased by Victorian owners Merv and Meg Butterworth and is likely to campaign in Australia after enjoying a spell, she said.
"It was a great result since we are losing him."
Barclay’s run into the race on Duke Of Wellington came after he made a crucial move to push out rival Convair Hustler with a lap to run.
The move resulted in Duke Of Wellington tracking runner-up Hail Christian for the final 900m before he slingshotted off his back with a sharper sprint in the straight.
"It was a great drive," Pearson said.
Barclay looks a good chance to the 2029 Southern Supremacy Stakes, as his three wins in the race have come in 11-year invervals. His supreme drive on Duke Of Wellington added to his wins in the race with Corumba in 1996 and Looksaflyer in 2007.
The only thing that was a suprising about yesterday’s group 3 2yr-old event was the winning time.
The race was predictably won by Mark Purdon and Natalie Rasmussen-trained favourite A Bettor Act.
Despite not having any rivals come up and challenge him in the lead during the event, A Bettor Act smashed the Ascot Park 2yr-old track record.
His 2.40.6 time obliterated the previous mark of 2.43.7 set by Aloka in the same race last year. Mosgiel trotter Pres The Belle provided driver Dexter Dunn with one of his four wins on yesterday’s Diamonds Day card.
Dunn had the Darryn Simpson-trained mare freewheeling in front and she dealt to her rivals who were strung out and and finishing with big intervals between them. The victory was Pres The Belle’s third career win and clearly the biggest in her 14-start career.
Dunn’s four wins put him on 154 wins for the season, 26 behind premiership leader Blair Orange.
Yesterday’s Country Cups Series heat for older pacers featured surprise flops by leading 4yr-old mares Somejoy and Delishka.
The two pacers, along with fellow favourite Royal Bengal, could not catch leader Swamp Major who won his first race in more than two years.
