Lombard Street to a China Orange
Long odds. Lombard Street, London, is the centre of great banking and mercantile transactions. To stake the Bank of England against a common orange is to stake what is of untold value against a mere trifle.
“`It is Lombard Street to a China orange,' quoth Uncle Jack.” —
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Lombard Street to a China Orange from Infoplease: