I have learned a lot from reading historical romance novels. Unfortunately, one of the primary things that I have learned is incorrect. During the Napoleonic Wars, many Englishmen were spies, as many as a quarter to a third, apparently. Not only that, but a lot of them were seemingly very bad at it and got captured by the French. Not all of these fictional English spies were awful enough to be captured, but enough were to make me wonder how, if this was the quality of the opposition, Napoleon was ever defeated. Okay. Okay. It's true that the villainous French captors often let slip Very Important Information during their sessions questioning/torturing their British captives. And these captors almost inevitably met their deaths at the hands of their erstwhile captives. But that doesn't excuse the fact that they got caught in the first place.
I think the book that finally made me roll my eyes at the frequency of the capture of English spies was A Lady's Revenge by Tracey Devlyn. Not that the book itself is deserving of eye-rolling, just that it started right off with the rescue of a captured spy called "the Raven" (which about half of them are in these novels), and I had just finished reading Mary Jo Putney's No Longer a Gentleman, which is also about a captured spy. It was just too much, too close together for my little brain to take. Both novels are really quite good, but I don't recommend reading them back-to-back. Aside from likely making you question the competence of 19th-century British Intelligence agents, these aren't exactly fun, frothy reads. Of course, they both end with Happily Ever After, but the journeys to get there take some dark and twisted paths.
In Mary Robinette Kowal's Glamour in Glass (the sequel to my much-beloved Shades of Milk and Honey), Jane and Vincent head to Belgium on their honeymoon and there's some espionage involved and a prison break using the glamour (magic) of the title.
And then there are the novels of Joanna Bourne, which feature both French and English spies in various configurations but all working against and/or fleeing the Revolution or Napoleon. A French prison is actually the nexus at which the diverse storylines of her novels converge. (Well, prison and the character of Hawker, who I believe shows up in the pages of all four books.)
The fact of the matter is that there couldn't have been that many spies working against Napoleon. But even if there were, I can't believe that such a large portion of them got caught. In time, I'm sure I'll be able to suspend my disbelief once again. Because as clichéd and unbelievable as I may find this storyline, I'm still a sucker for it.