Revealing mistake: At the start, the background of the country going by when on the train is very obviously a fake. It sticks out like a sore thumb.
Only a Story - S5-E2
Continuity mistake: When Margaret comes back in the evening, there are wallpaper rolls on the dining room table that are no longer there in the next shot.
The Executioner's Song - S6-E1
Other mistake: The lady opposite wants to watch the large TV through the Meldrews' window, but when you see the windows, they are frosted and it would be impossible for her to see the TV. (00:16:30)
The Pit and the Pendulum - S4-E1
Revealing mistake: The inside of the kitchen set doesn't match the external shot of the real location when looking at the inside of the kitchen door. The studio has a flat wall with green patterned wallpaper, where the real kitchen has a cupboard, white handles and the worktop directly next to the door side.
Chosen answer: The episode is 'The Pit and the Pendulum' The first episode of series 4.
James Ransford ★