1900, Allen, F.M. , London’s Peril 

F.M. Allen [pseud. of Edmund Downey] (1900) London’s Peril

A plan by the French to invade through a Channel Tunnel.

“Then it is understood. The secret which I possess, and which I desire to sell,” said M. Dupont, “is known to very few, and to nobody else, in all human probability, who could or would impart it to your Government. If we come to terms, my life will not, it is possible, be a very valuable asset. Yet, I persuade myself that my countrymen will hereafter see that I acted in their interests. I am ready to disclose my secret to your lordship, and the price I shall ask will at least convince you that I consider my information to be, as I have already described it in my letters, the most important ever offered to the English Government.”

“I am afraid,” observed his lordship, ” that you are somewhat slow in coming to the point. With what, or whom, is your secret concerned ? “

” The seizure of London by France,” said M. Dupont.

Full text at: https://openlibrary.org/books/OL7249407M/London%27s_peril