Complex sentence: He began his political career in 1974 when he was elected to Haringey Council, and also served as Secretary of the Islington Constituency Labour Party; he continued in these roles until his election as the MP for Islington North.
Split into simpler sentences: He began his political career in 1974 when he was elected to Haringey Council, and also served as Secretary of the Islington Labour Party. He continued in those roles until his election as the MP for Islington North.