Complex sentence: It was during a meeting at the White House when Churchill was handed a signal that Tobruk had fallen he then burst into tears, the US President stood up and approached Churchill and said to him "What can we do to help?".
Split into simpler sentences: It was during a meeting at the White House, when Churchill was handed a signal that Tobruk had fallen, that he burst into tears. The US President stood up, approached Churchill and said to him "What can we do to help?".