Wise as the Mayor of Banbury
A blundering Sir William Curtis. The mayor referred to insisted that Henry III. reigned in England before Henry II.
The following is a fact which happened to myself in 1880. I was on a visit to a country mayor of great wealth, whose house was full of most exquisite works of art. I was particularly struck with a choice china figure, when the mayor told me how many guineas he had given for it, and added, “Of course you know `who' it is meant for. It is John Knox signing Magna Charta.”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Wise as the Mayor of Banbury from Infoplease: