Catharine Arnold is an author, journalist and popular historian who joins our show for the second time. With her 'London Trilogy', Catharine has explored the darker sides of the capital from Roman times through to present day. Starting with London's dead in 'Necropolis', via its insane in 'Bedlam', Catharine finishes her trilogy with 'City of Sin', a book that focuses squarely on the history of London's shocking sexual underground.