Caravan towing lights with front cover protector

Can anyone tell me if it is a legal requirement to travel and night time or in low light condtions with the front side lights clearly visible.

I have just purchsed one of the front cover travelling protectors.

The instructions contained state that I have to cut the cover where my side lights are to make them visible whilst towing at night.

This is ok for this van but I am sure if I purchased another van they would not be in the same place, thereby leaving a hole.

If I have front side lights on my towing vehicle and rear lights on my caravan will this be legal?

regards David