I think it is important to stress, at least from a legal point of view, that this interpretation is their opinion; only a court can decide if you would actually be breaking the law.
If any fancies shopping themselves to the local constabulary and then paying for a good defence in order to get the law more clearly defined in the favour of horse owners, I’m sure we’d all be grateful. 
BarnetEngineer:
I think it is important to stress, at least from a legal point of view, that this interpretation is their opinion; only a court can decide if you would actually be breaking the law.If any fancies shopping themselves to the local constabulary and then paying for a good defence in order to get the law more clearly defined in the favour of horse owners, I’m sure we’d all be grateful.
I’d oblige but I don’t have a horse box so I’ll have to leave it to you … sorry.
Don’t forget to post a link to the court case 
If you had a screen connected to 2 cameras, one as a reversing camera and one pointing at the horses, you’d be very unlucky to get prosecuted IMHO