He was the Convener of the Justice Committee, having previously held the portfolio of strategy, communities, social security, the constitution and equalities.

Professor Douglas Brodie, former head of the School of Law at the University of Edinburgh, has also joined this project.

[1][10] On 17 July 2020, Tomkins released a statement announcing his intention to stand down as an MSP at the next election due in May 2021 for personal reasons related to work and family.

[11] In April 2021, Tomkins wrote an article in The Spectator calling for a new law to define when constituent nations of the United Kingdom could hold independence referendums.

[13] In 2022, following the mini-budget of Liz Truss and Kwasi Kwarteng, Tomkins said it was "inevitable" that the Conservatives would lose next election.