"My two-year-old daughter was killed by falling masonry"

Four years ago, two-year-old Greta Greene was hit by a piece of falling masonry while out with her grandmother. She later died in hospital. Her father Jayson has written a memoir Once More We Saw Stars. He told Jenni Murray how he coped with his grief in the initial aftermath, how his emotions have changed and what he says when someone asks him how many children he has.