A hat-trick from former Irish hockey player Mark Gleghorne gave GB a 3-0 victory over Ireland in an uncapped friendly match at Bisham Abbey.
Gleghorne scored three penalty corners in the first half with the Irish competing well in an even second half.
The sides meet again on Tuesday and Thursday in a three-match series which is vital preparation for both nations ahead of the Olympic Games in Rio.
"The second half was much better," said Ireland coach Craig Fulton.
"We upped the speed and were more aggressive."
It's the first time the teams have met since the bronze medal match at the Eurohockey Championships in August 2015, which Ireland won 4-2.