The first semi-final of the Mastermind series comes from Blackpool Tower Circus. In the spotlight are Richard Heller from London, Ross Stafford from Harrow, Alan Whitaker from Penzance and Matthew Potter from Limerick. Their specialised subjects are British political history 1918-40, the ghost stories of MR James, the Wars of the Roses, and Irish political history 1870-91. Magnus Magnusson asks the questions.