He enjoyed a hugely successful time with Otago Boys', winning the Highlanders' first XV competition in each of his seasons with the school as well as scoring a record number of points in a year, more than 450 in 2014.
[6] After leaving school, he began playing for the Harbour Hawks in the local Otago club rugby competition.
In total he played 6 games in his first year at provincial level as the Razorbacks finished 3rd on the championship log before going down comprehensively to Wellington in the competition's semi-finals.
[3] In April 2022 it was announced that Tomkinson had signed for the Welsh club Dragons RFC in the United Rugby Championship for the 2022/23 season.
In October 2024 it was announced that Tomkinson had signed for the Western Force in the Super Rugby Pacific competition for the 2025 season.