Mary Wimbush (Aunt Agatha) and Graham Seed (Sidney) appeared together for many years as mother and son, Julia and Nigel Pargetter in The Archers.
The locomotive that is briefly seen in the opening sequence is a GWR (Great Western Railway) 6400 Class No. 6412 pannier tank engine.
In his column in the Telegraph, Stephen Fry writes about the time spent filming this episode on location in Sidmouth. This column was reproduced in Paperweight (1992), an anthology of Fry's columns, reviews, and miscellaneous scripts from the 1980s and early 1990s.
The theatrical musical portrayed in this episode--Woof, Woof--opened on Broadway on Christmas Day, 1929, and ran until Feb. 1 the next year.
The hire car that Jeeves and Wooster arrive at the hotel from the train station in has the number plate PG 9441