Factual error: Major Robinson threatens Steed with a revolver equipped with a silencer. A military officer would certainly know better. Though it's a common movie and TV cliché, it is a glaring error. Revolvers are open-chambered, allowing sound to escape out the back of the barrel - so they can't be silenced. There are rare exceptions if the gun is heavily modified to close the open chamber gap, but that does not apply to the weapon featured here. (00:46:00)
Continuity mistake: The cigarette lighter Robinson uses to set the incriminating papers alight disappears from the desk as he makes his phone call. (00:21:30)
Visible crew/equipment: A large round studio light is visible in the lorry's door just after it strikes the motorcyclist. (00:02:00)
