Brian was a police officer for over 30 years rising to the most senior levels of the Metropolitan Police at Scotland Yard. He was widely praised for his role as police spokesman following the terrorist attacks on London in 2005. Brian was also the most senior openly gay police officer in the UK.
Brian later stood as the Liberal Democrat candidate for Mayor of London in 2008 and in 2012.
Brian was appointed to the House of Lords in September 2013.
In 2015 he was appointed as Liberal Democrat Home Affairs Spokesperson in the Lords, in October 2016 he was made Shadow Secretary of State for the Home Department under Tim Farron.