Having represented both Team GB and Team Scotland as an elite athlete in the Olympics, Commonwealth games, World and European championships - where he famously won a gold medal, he then participated in the campaign for Scotland to remain part of the UK in 2014, Brian was asked to stand for the Scottish Conservative and Unionist Party in the Kilmarnock and Loudon seat at the 2015 Westminster General Election where he came third with the largest number of Conservative votes in the constituency since 1992.

Brian was elected as a Member of the Scottish Parliament for South Scotland in 2016 and served as the party's spokesperson for Public Health Mental Health, Wellbeing & Sport. At Holyrood, he was a member of the Health & Sport Committee and the Public Petitions Committee. He was also one of the parliament's most regular speakers and was among the highest ranked MSPs in session 5 for number of First Minister's Questions.

His particular area of interest is in how Scots from all backgrounds can have access to as many opportunities as possible to be more active. As the NHS faces a growing burden from preventable disease, it's more important than ever that there is a focus on trying to improve our health as a nation.

Brian was re-elected in 2021 as a South Scotland Regional MSP and has been appointed Shadow Minister for the Environment, Biodiversity and Land Reform. He also serves on Holyrood's Covid-19 Recovery Committee.  Alongside Dr Sandesh Gulhane MSP he is co-author of Scottish Conservatives Health & Social Care Policy proposal.