The Lunatic at Large by J. Storer Clouston

The best-bred lunatics in England live in Clankwood, and Francis Beveridge is that community's newest resident. Rather than attending the asylum's Saturday dances, though, Beveridge goes on the lam in London. And thus, when a traveling German noble finds himself at the luxurious Hotel Mayonnaise without a guide to England's customs, who better to escort him than the amnesiac Englishman who materializes by his side? Beveridge provides the German with much useful knowledge, like giving a splendid tutor in bringing rail stations to a standstill, revealing the best way to fake a rabies attack, and showing how to crash London's most exclusive clubs — quite literally. A much-loved Victorian comic masterpiece, this is the original anarchic novel that ushered in the age of Wodehouse and Waugh.