The Swoop! - P. G. Wodehouse

The Swoop! tells of the simultaneous invasion of England by several armies — "England was not merely beneath the heel of the invader. It was beneath the heels of nine invaders. There was barely standing-room." (ch. 1) — and features references to many well-known figures of the day, among them the politician Herbert Gladstone, novelist Edgar Wallace, actor-managers Seymour Hicks and George Edwardes, and boxer Bob Fitzsimmons. (Summary from Wikipedia)