Complex sentence: He became Leader of the Conservative Group on Birmingham City Council in 2003, and following the city-wide elections in 2004 has led the Council in what he terms a'progressive partnership' with the Liberal Democrats.
Split into simpler sentences: He became Leader of the Conservative Group on Birmingham City Council in 2003, and Leader of the Council in 2004. Following the city-wide elections in 2004 Whitby has led the Council in what he terms a'progressive partnership' with the Liberal Democrats.