Revealing mistake: Episode Aired 12th December. In the laundrette a shelf had fallen off the wall and Dot Cotton needed someone to fix it. You could see the wall was false, as every time Dot touched the shelf, the wall was wobbling. Later same episode Martin Fowler fixed the shelf he said something like "the wall will fall down before the shelf does" - very true.
Revealing mistake: In an episode when Stacey was in the Minute-Mart and she was begging Patrick and Yolande to give her her job back, a man can be seen standing in the doorway. But when the man looks up and sees the camera, he soon scrams out of the shot.
Revealing mistake: In the legendary episode where Steve Owen dies, the car somehow manages to get flipped over onto its roof. Only a bomb going off would create such an effect, not just the tank going up.
Revealing mistake: 3/6/08: When Dawn is chasing after Keith while pushing Summer (her daughter) in the pushchair, it is obvious that there is no baby in the pushchair, even though she can be heard crying.
Revealing mistake: In the episode where the "young" group of characters leaves for Scotland on New Years Eve, they're supposedly leaving at 7 in the morning, yet the sun is shining high in the sky during a deep winter's day.
Revealing mistake: Whenever the characters have a drink in a mug (at Ian's cafe or at their house etc), there is never anything in the cup.
Revealing mistake: 14/3/23 In the final scene when Kat slams the front door after leaving Stacey's house the wall shakes.
Revealing mistake: Episode aired 06/05/2016. Steve (Ronnie's stalker) pulls out a folder of newspaper clippings concerning Ronnie's baby-swap case. It shows up close an "article" which is seemingly legit when reading the first few lines...only to show the same sentence repeatedly, merely the information having been rephrased. Either the Eastenders-verse bears some rather incompetent and careless journalists, or the writers of the soap were simply too much too bone-idle to write up even the most mediocre of articles. (00:28:05)
Answer: Most likely a mistake by the set designers or it's a recycled set which already had the switch on (they just repaint and add other fittings).
At my workplace there is a two-gang switch with a three-gang switch underneath it, one of which is for the shop lights, the other four have no apparent use.