There was alway a problem identifying men in the valleys, so many Davids, (all known as Dai) that nicknames were automatic. There was Dai eighteen months (he'd lost half a ear playing rugby) Dai Bungalow (he was so thick, people joked he had "bugger all upstairs"). Many named from their professions, such as Dai the Milk, and Dai the Post.
So it happened that Ivan came on a secret mission to the valleys, Looking for David Jones. The first door he knocked at was answered by a young man who answered to the name of David Jones, and Ivan said "Red Sky at Night, Shepherd's delight".
The young man replied "Oh no, you want Dai the Spy at No 43".