Deliberate mistake: When Joey and Jonathan get in Joey's car at Metropolis (just before heading to the police station), the car has headrests. When they get to the police station, see Lance Gessler leaving and then follow him, the car no longer has headrests. Obviously removed so as not to obstruct the actors.
Jonathan Creek (1997)
1 deliberate mistake - chronological order
Starring: Alan Davies, Caroline Quentin, Stuart Milligan
Plot hole: Why on earth would a sleazeball like Adam Klaus be worried about news of a one-night stand being revealed? He'd welcome the publicity, if anything. Anyone threatening to go to the papers with news of a bit of rumpy-pumpy with him would be wasting their time.
Madeline Magellan: Enough with the pedanticism and let us eat.
Jonathan Creek: The word is pedantry.
Question: What exactly did Jonathan and Maddie give to the tramp in exchange for information?
Answer: It was actually mouthwash.
Chosen answer: It was a bottle of turpentine.
Methylated spirit, always coloured purple.