Brewster came to prominence in the
Ulster Unionist Party (UUP) as a close associate of
David Trimble. Unenthusiastic about
Jim Molyneaux's leadership of the party, Brewster backed Trimble's successful candidacy in the
September 1995 leadership election. Brewster was already the Secretary of the East Londonderry Association of the party, and Trimble assisted him in winning election as one of the party's honorary secretaries in 1996. Brewster claimed that Trimble also offered to help him take over as the Member of Parliament for
East Londonderry from
William Ross, a leading figure in the UUP but a critic of Trimble. However, Brewster did not want the role, He worked with
Peter King and Dean Godson on the UUP's "Strand I" team at the talks which led to the
Good Friday Agreement. Brewster was also active in the
Orange Order and, like most UUP members who were prominent Orangemen, he became critical of Trimble's leadership, and opposed the Good Friday Agreement. He joined the oppositionist Union First Group, and left the party in 2003 to join the rival
Democratic Unionist Party. and served as president of the Roe Valley Chamber of Commerce from 2013-2016. He was also vice chairman of
Limavady United Football Club and President of the William F. Massey Foundation. ==References==