William Leo Franklyn (22 September 1925 – 31 October 2006) was a British actor, perhaps best known for voicing the "Schhh... You Know Who" adverts for Schweppes from 1965 to 1973. He also performed on stage, film, television and radio, taking over from Peter Jones as "The Book" (the narrator) in the third, fourth and fifth radio series of The Hitchhiker's Guide to the Galaxy. He is also known for his portrayal of Sexton Blake for BBC Radio 4 in 1967.