Ah, Julian!

Leonard Patrick O'Connor Wibberley, who also published under the name Patrick O'Connor, among others, was a prolific and versatile Ireland-born author who spent most of his life in the United States. Wibberley, who published more than 100 books, is perhaps best known for five satirical novels about an imaginary country Grand Fenwick, particularly The Mouse That Roared (1955). Wibberley's adult and juvenile publications cut across the categories of fictional novels, history, and biography. He also wrote short stories (several published in The Saturday Evening Post), plays and long verse poems. - Wikipedia