If you are a Downton Abbey fan, you will love Belgravia. It was also reminiscent of a Georgette Heyer Regency novel. Fairly early on I guessed what would happen but this didn't diminish my enjoyment by one whit. (What is a whit anyway?)
The author also wrote the script for Downton Abbey. The style is clear and direct and pretty close to the period. The formative events of the book occurred at the famous ball held on the eve of the Battle of Waterloo.