At just 22'34m, this is the shortest episode of Grandad.
Every season of Grandad was repeated in full the following year after broadcast. The viewing figures for a repeat of this episode on 12th August 1981 were 3.64 million.
Grandad reveals that he has an "Auntie Flu" after being reminded of her by a chimpanzee toy.
The character never appears in the series, so it's unclear what "Flu" would be short for, or whether it's a mistake in pronunciation - though the names "Florence" and "Flora" were among the most popular girl's names at the start of the 20th century.