Deliberate mistake: In the shot where we see the cars in front of Victor's (shortly after Victor gets out of the car and gets back in when the traffic starts moving) you can see that after the white car on the right that there are no more cars even though the episode takes place in a traffic queue! If you listen to the commentary on the DVD, writer David Renwick points out the mistake and informs us that they had a limited number of cars for the shot. (00:11:25)
Revealing mistake: A minute or so after the health and fitness instructer dies, we see her lying flat out on her back. If you look carefully, you can see her chest moving up and down and breathing despite being dead. (00:13:05)
Trivia: The Christmas Special that aired in 1995, was initially intended as the series' finale, and would have seen Victor being killed while saving Margaret who was being attacked by a madman. The 1997 special was then intended to end the series with Margaret dying from a heart attack brought on from the strain of Victor's misadventures, but on both occasions the production crew got cold feet. It wasn't until the final series in 2000 that the team, in David Renwick's words, "plucked up the courage to kill Victor."