Just take care boys ....
I think you may find that Contruction and Use Regs say that all motor vehicles MUST have the wheels covered and guarded in such a way as excess mud and spray isn't thrown up. There will be laid down definitions and standards.
The vehicle makers will have had prototypes passed, and in the case of Landies I feel pretty sure they had to fit decent mudflaps to get a pass. I mean, imagine a Defender 90 with no rear flaps. Bad luck being behind that on a muddy road!
Therefore, as we all have a sort of legal obligation to MAINTAIN our cars in that sort of intended condition, we COULD get in bother if we got pulled for no rear flaps and gave a cops a lot of cheek. I think a court COULD convict under C & U Regs for inadequate mudflaps and poor anti-spray protection.
CharlesY