Gogglebox's William Hartston makes his Grand National prediction.

Apr 03, 2014, 08:57 AM

Teaforthree is the 9-1 favourite to become the first Welsh-trained winner since 1905 at this weekend's Grand National. But a Cambridge mathematician thinks he has a formula to calculate the winner, and he disagrees. William Hartston - or Gogglebox's Bill - explains his method to Andie..