Complex sentence: While in the House of Commons he became a convert to catholicism, and his political activity largely aimed at safeguarding religious education in Ireland (Hansard, 3rd ser. lxxx.1142--3).
Split into simpler sentences: While in the House of Commons he became a supporter of catholicism. His political activity largely aimed at safeguarding religious education in Ireland (Hansard, 3rd ser. lxxx.1142--3).