Complex sentence: Chamberlain was offered no further posts during Lloyd George's premiership, and when Bonar Law resigned as party leader, Austen Chamberlain took his place as head of the Unionists in Parliament.
Split into simpler sentences: Chamberlain was offered no further posts during Lloyd George's premiership. When Bonar Law resigned as party leader Austen Chamberlain took his place as head of the Unionists in Parliament.