In this episode there is an assassination attempt by Edward Oxford which indeed did happen. We see the London Peelers (police) for the first time properly in this series. They have incorrect armbands (Should be 2 blue stripes not 3), they are wearing belts (which were not added to the uniforms until 1853) and truncheon hangers attached to the belts. Truncheons were kept in the tailcoat and hangers were not introduced until 1862-1864 when the uniform changed to frock coats and cockscomb helmets. The collar insignia is incorrect with the wrong lace and just a number (copied from an image of a Birmingham City Police tunic at present in a museum in Birmingham). There were 10 divisions and each peeler would have had a divisional letter followed by their number. Buckingham Palace was covered by A division so for example the collar number should be A.123. The A was circled by tress and the number was within a lozenge shaped tress (The tress was dropped in 1844). The biggest boo-boo is the reporting of the investigation by a police sergeant directly to the queen. I would very much doubt a police sergeant would have been given such an audience...Home Secretary or Chief Commissioners at the very least.