Perhaps best known as one half of a husband and wife duo who have written more than fifteen psychological thrillers under the name of Nicci French, author Nicci Gerrard is an award-winning journalist in her own right. Her books appeal to readers who acknowledge that we all inhabit the fringes of some very dark places. Unafraid to cover difficult topics, her book Soham asks what we can learn from a recent notorious child murder case in the UK and questions how our response to evil is often manipulated by the media. Her latest book What Dementia Teaches Us About Love is a candid and thought-provoking investigation into the medical, moral and personal issues caused by a condition that now touches millions of us but that we still find it hard to speak about. She talks to George Alagiah.