John and his class visit the Tower of London, where he loses his pet mouse. He falls asleep during a lesson on electricity, but with some help, he learns about it, invades the Tower, and saves his pet.
Mark Dightam
as John
Robert Eddison
as Nick
Helen Weir
as Mrs Saunders
Brian Worth
as Mr Saunders
Esmond Knight
as Doctor
Laurence Carter
as Schoolteacher
Patrick McAlinney
as Supreme Beefeater
Lem Dobbs
as Munro
