|Guest appearances of Johnny Ball|
|First appearance||15 October 2007|
|Last appearance||19 October 2007|
|Episodes with Johnny Ball|
Johnny Ball is a guest on Countdown. He is a TV presenter, famous for popularising mathematics. He is one of the few Dictionary Corner guests to have done worse than Carol Vorderman on Strictly Come Dancing, although he was at a disadvantage due to his partner getting injured in training.