Towbar Blocking numberplate - Legality?

[Stoofa]

I was following some Nissan yesterday.
I noticed it had a towbar on, however this was positioned right over the numberplate.
You could clearly see:

AK & "xxx" at the end.
However the two digit date identifier was totally blocked - couldn't see either of the numbers.
Now I know even with just the first two letters and last three you are lead to a relatively small number of vehicles.
And I guess further investigation - just how many of those finite vehicles were Nissan.

But still, a blocked numberplate is a blocked numberplate and I believe has an offence code?

Just interested.

[Stoofa]

So I guess in the case of the Nissan I followed.

(4)It is a defence for a person charged with an offence under this section to prove that he took all steps which it was reasonably practicable to take to prevent the mark being obscured or rendered not easily distinguishable.

Might be a possible defence.

Nissan put the space for the rear numberplate at the bottom of the car.
The owner needed a towbar and so there was no option but for the toebar to be placed in front of the plate.