"As lazy as Ludlum's dog, as laid him down to bark."

This comparison is so general and familiar in South Yorkshire (Sheffield especially) as to be frequently quoted by the first half, the other being mentally supplied by the hearer. There must, of course, be some legend of Ludlum and his dog, or they must have been a pair of well-known characters, to give piquancy to the phrase. Will any of your readers who are familiar with the district favour me with an explanation?