Complex sentence: Most notably, he joined the growing support in the colony for self-governance, which was already a major political issue; the New South Wales Legislative Council had been reformed in 1843 to include elected members for the first time.
Split into simpler sentences: Most notably, he joined the growing movement in the colony for self-governance. This was already a major political issue; the New South Wales Legislative Council had been reformed in 1843 to include elected members for the first time.