Saved By a Stranger BBC2, 9pm
Anita Rani looks at the stories of ordinary people caught up in the biggest events in living memory, and the person who changed their lives. It begins with Karl, a trainee clinical psychologist who was a passenger on the first carriage of the Piccadilly Line London Underground train – one of the four targets of the 7/7 bombings. After the bomb exploded, Karl was comforted by a woman.