Complex sentence: Earlier that day Churchill had lunched with Anthony Eden, the Secretary of State for Dominion Affairs, and Kingsley Wood, the Lord Privy Seal, who been a friend and colleague of Chamberlain for nearly twenty years.
Split into simpler sentences: Earlier that day Churchill had lunched with Anthony Eden, the Secretary of State for Dominion Affairs, and Kingsley Wood, the Lord Privy Seal. Wood had been a friend and colleague of Chamberlain for nearly twenty years.