Southampton's Wise Sons
In the early part of the present century, the people of Southampton cut a ditch for barges between Southampton and Red-bridge; but as barges could go without paying dues through the “Southampton Water,” the ditch or canal was never used. This wise scheme was compared to that of the man who cut two holes through the wall - one for the great cat and the other for its kitten.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Southampton's Wise Sons from Infoplease: