When all of the British Secret Service's active undercover agents are exposed during a funeral and subsequently eliminated, the agency is forced to call upon an unlikely backup in the form of Johnny English. English, an inept MI7 employee with dreams of being their top spy, is given the chance to prove himself as he is promoted to the position of Britain's last standing secret agent. With the help of his assistant Bough, English embarks on a mission to safeguard the recently restored Crown Jewels and discover who is behind their theft.

As English clumsily and comically navigates the world of espionage, he zeroes in on a French entrepreneur, Pascal Sauvage, who has been granted an honorary title by the Queen of England. English stumbles upon a plot that goes beyond the Crown Jewels, as Sauvage's intentions appear to threaten the very throne of England. With his unorthodox methods and sheer luck, English must overcome his ineptitude and prevent a royal disaster, relying on gadgets, his sidekick, and a mysterious woman who captures his interest. His investigation leads him through a series of misadventures as he tries to expose the conspiracy and save the kingdom from an impending coup.