techiedoc said:
I am planning to buy an in-car Snowman lit by the car cigarette lighter.I wonder if it would be legal to place it behind the back seats for urban driving(as opposed to motorways).
As I understand it, it depends what colour it lights up.
The regulations basically say that you must not show any red light to the front (with a few exceptions) and you must show
only red light to the rear (with a long list of exceptions -- which strangely does not mention either snowmen or Christmas decorations in general (surely a oversight by the Minister of Transport

)).
So if it is red, I think it should be OK, as long as you can't see the red light from the front, and as long as it's not bright enough to dazzle anyone.
Oh, hang on... it's not allowed to "automatically emit a flashing light" either.
See
The Road Vehicles Lighting Regulations 1989 for the full details of these tedious rules.