Complex sentence: His political career began when he was elected to Haringey Council in 1974, later also serving as Secretary of the Islington Constituency Labour Party (CLP); he continued in these roles until he entered the House of Commons as an MP.
Split into simpler sentences: His political career began when he was elected to Haringey Council in 1974 and later was secretary of the Islington Constituency Labour Party (CLP). He continued in both roles until he entered the House of Commons as an MP.