Brenda Cross, of Northland, coaches the Kiwi team which includes siblings Kevin (Scotland), Denise (Waikato) and Jamie (reserve, Waikato) Egging, Danny Kopa (Northland) and Nicole Hope (Hawke's Bay).
"It's a different competition because we'll be riding on borrowed horses," says Adamson who was a reserve in the Bay-hosted mounted games in 2013 which the hosts won.
He had to overcome a field of 46 in a pony relay format to clinch the British individual crown last month.
Adamson was tied equal on 42 points with County Royal Berkshire teammate Rory Capel with Katie Barrett setting the pace two points ahead of the pair.
The male riders needed to win the 10th and final race for maximum points to displace Barrett.
"I was quite lucky it was a speed race and Trigger quite fast," he says, emphasising his mount's age is relatively "middle-aged" in mounted games and ideally equates to more experience.
Capel and Barrett had to have a run-off to decide the second place and the former prevailed.
Adamson, who lives with English girlfriend and fellow mounted games competitor Mercedes Lock, has bracketed in the Royal Welsh Show after his stint in Kentucky.
"It's the main agricultural show in Bulith so the opportunities [to compete] are great here," he says before quickly qualifying the winters are unforgiving and summers "not like the Hawke's Bay ones".
"It's June/July and raining here."
The first Bay rider and youngest to win the Mounted Games NZ Open two years ago, helps out at his girlfriend's family farm where he has another horse, Prince Caspian, a four-year-old Arabian he bought recently.
"He was a lot of work to start with but he's good to ride now.
"I don't think he had even been cantered with on the back when I got him."
Adamson, who plans to attend university in a year to pursue a degree in business management, thanks his family and friends in the Bay for their ongoing support of his sporting acquisitions.