Complex sentence: Prime Minister Tony Blair made Miliband Parliamentary Secretary to the Cabinet Office in May 2006 and when Gordon Brown became Prime Minister in 2007, he appointed Miliband Minister for the Cabinet Office and Chancellor of the Duchy of Lancaster.
Split into simpler sentences: Prime Minister Tony Blair made Miliband Parliamentary Secretary to the Cabinet Office in May 2006. When Gordon Brown became Prime Minister in 2007, he appointed Miliband Minister for the Cabinet Office and Chancellor of the Duchy of Lancaster.