So popular was Mullard's character that a sequel — Yus, My Dear — was broadcast in 1976, in which Wally and his wife Lily (Queenie Watts) had moved out of their caravan into a council house.
In Europe, the principal method of numbering vacuum tubes ("thermionic valves") was the nomenclature used by the Philips company and its subsidiaries Mullard in the UK, Valvo in Germany, and Dario in France, from 1934.
Mullard joined the IEE as a student member in 1903, became a full member in 1910, and a fellow of the IEE in 1928.