Charles Darwin's mother Susannah Wedgwood died when he was just eight, and he could never remember her face - until he discovered a long-hidden portrait of her as a young woman. Hear Darwin's great-great-grandson Randal Keynes explain why finally seeing this miniature of his mother (now in the collection of the Fitzwilliam Museum) was so significant for the great naturalist, and why portraits of loved ones were so important to both the Wedgwood and Darwin families.