Robin was elected as the UK's first ever Green Parliamentarian in the Scottish Parliament elections in May 1999, representing the Lothians. In May 2007, he was re-elected for the third time to the Scottish Parliament, representing the Lothians. 

As well as being Co-Convenor of the Scottish Green Party, Robin is also Convenor of the Scottish Parliament's Cross Party Group on Architecture and the Built Environment, Convenor of the Scottish Parliament Renewable Energy Group (SPREG) and Convenor of the Cross Party Group on Children and Young People. Robin is on the Board of several theatre companies and is keen on promoting outdoor education, art, music and drama.

He received Best Politician of the Year Award from the Scottish Renewables Forum in 2002 and accepted Election Performance of the Year Award on behalf of the Scottish Green Party at the Scottish Politician of the Year Awards 2003.

A former teacher, Robin was Rector of Edinburgh University from 2001-2003 and since July 2005 he has been Rector of the University of Aberdeen.