Classicly

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. 

Author's Preface:

It may be thought by some that in the pages which follow I have painted in too lurid colours the horrors of a foreign invasion of England. Realism in art, it may be argued, can be carried too far. I prefer to think that the majority of my readers will acquit me of a desire to be unduly sensational. It is necessary that England should be roused to a sense of her peril, and only by setting down without flinching the probable results of an invasion can this be done. This story, I may mention, has been written and published purely from a feeling of patriotism and duty. Mr. Alston Rivers' sensitive soul will be jarred to its foundations if it is a financial success. So will mine. But in a time of national danger we feel that the risk must be taken. After all, at the worst, it is a small sacrifice to make for our country.