London, with a short excursion to Paris during the Reign of Terror
Swashbuckling hero hardly comes to mind when mentioned in conjunction with one of history's darker moments in time, yet it is exactly what one thinks of when the hero is the Scarlet Pimpernel. Daring, adventurous, secretive, romantic – The Scarlet Pimpernel embodies everything a typical British hero is often portrayed as (but, like Americans, hardly ever in reality is :) ). If you like sitting on the edge of your seat and flying through a book just to see whether the hero will live or die and what happens to his beautiful wife, then this book is for you. And yes, I know that the book's author isn't really British, but as she did live there for most of her life, it seemed enough to make her an honorary inclusion to my list.
The book's wiki page
Baroness Orczy's bio