"Doctor Syn" by Russell Thorndike.
Doctor Syn is the first in the series of Doctor Syn novels by Russell Thorndike. It is the first appearance of the Reverend Doctor Christopher Syn, the vicar of the little town of Dymchurch. Although it is the first book in the series, the events described in it are preceded by the following books.
This book was completed as part of the Tenth Anniversary Contest.
To those who have small knowledge of Kent let me say that the fishing village of Dymchurch-under-the-wall lies on the south coast midway between two of the ancient Cinque ports, Romney and Hythe.
In the days of George III, with Trafalgar still unfought, our coast watchmen swept with keen glasses this broad bend of the Channel; watched not for smugglers (for there was little in Dymchurch to attract the smuggler, with its flat coastline open all the way from Dover cliffs around Dungeness to Beachy Head), but for the French men-o'-war.