In the UK, what is the legal position regarding missing or obscured number plates?

Thank you all for answering. johnrichard9000 mentioned the Highway Code but I cannot find that reference on that website. I've thoroughly searched sites on number plates and the only references are to ensure the font and spaces between letters are within specification.

I have read no official documents relating to keeping the number plate legible through cleaning. There are mentions of not using tape or coloured screws to alter the way a number plate looks from a distance or to an ANPRS camera.

It'll be interesting to see if this car ever turns up again and if the problem has been corrected.

Certainly the woman I spoke to on the telephone seemed uninterested and asked me five times if I wanted to report the vehicle, even though I had stated at the beginning of the conversation that I was phoning to report a vehicle for failing to display a legible number plate.

There are many folks who cite fines and penalty points or non-endorsements in forum groups but no official rules seen.

@ Old Cynic - you are correct, "moderate police presence" is very descriptive. I would prefer "effective" over moderate but at times I feel it is more "police apathy" than "police presence".

I have been the subject of police interest many times over the years. When I have been the victim of a crime, they were not interested beyond me signing some forms and leaving.

Where I have been approached by constables, I have been minding my own business or engaged in lawful pursuits and they just have to tell what I could have expected if I had "parked six inches over" / "not taken due care and attention" and other minutiae. And they do not like it when I can quote the rules to them. They feel the need to repeat them to me for their own benefit.

Just my personal experience.