Hole in One - S4-E3
Revealing mistake: When the post is being posted through the door, you can see the letters appear in the letterbox and then wait a few seconds for Albert to hang his coat up before being pushed through. (00:01:00)
Hole in One - S4-E3
Revealing mistake: Uncle Albert is seen putting the post back through the letter box. If you watch the scene carefully, the letters appear to pull themselves through, no doubt with a helping hand from the crew.