Spencer is a married father of two teenage children who lives on the Eltham side of Shooters Hill. Spencer was first elected to Council in 2002 and has served on Greenwich Council as a Councillor for Eltham North ward since that time.

He was Deputy Leader of the Opposition from 2004 to 2006 and Leader of the Opposition from 2006 to 2015. Spencer works at Colfe's School in Lee where he is currently Director of Sixth Form and Head of the Government & Politics Department.