Despite having played most of his senior football in the
Brisbane Rugby League competition, Trewhella was ruled to be eligible to play for
New South Wales in
State of Origin after having first play senior football as a teenager in the
Newcastle Rugby League. He was selected on the bench for Game 1 of the
1988 State of Origin series at the
Sydney Football Stadium, and at hooker in Game 3 of the
1989 series at
Lang Park in
Brisbane where he scored his only try in representative football. Trewhella was also selected for the 1988 replay, but ruled himself out with a back injury. Following the 1989 Origin series (and thanks to injuries to
South Sydney's
Mario Fenech and
Balmain's
Benny Elias), Trewhella was selected as a hooker in the 20 man squad for the mid-season
1989 Kangaroo Tour of New Zealand. He played in 3 of the 6 games on tour, but was not selected for any of the tests against
New Zealand with coach
Bob Fulton preferring
Queensland and
Brisbane Broncos rake
Kerrod Walters in the role. Trewhella also played 2 games for
Country Origin in 1988 and 1989. ==Personal life==