"In theatrical parlance, that's known as the tail-end." -Rex Mottram
Through the help of Harry's ancient neighbor, Tom's learns his great granddad performed at the Regent's Theatre. The friends receive a backstage tour, and Tom is thrilled to learn that Harry acted opposite Laurence Olivier, in the role of "Greek soldier." His great-grandfather was mainly a comedic actor, known for his work as the back-end of a pantomime horse. The front half was played by Harry's partner, Sid Balducci; the pair worked together for two decades. Each year, they entered a pantomime horse race until they had a falling out.
As Pete and Tom leave the theatre with his great-grandfather's horse costume, the theatre manager reveals the truth: Chadwick and Balducci didn't split up because of Sid's gas problems-Sid had an affair with Harry's wife. After her husband died, Elsie married Sid and moved away.