A breach of the Highway Code is always compelling evidence of falling below proper standards of driving and so used in civil cases and those of careless driving etc. Some provisions are summaries of legal provisions.
My Highway Code, when I learnt, gave precise instruction on how to signal with one's whip when driving a horse drawn carriage or cart. Never had occasion to use that, though I can still remember it. But I had to know all the approved hand signals when driving a car and use them in the test. Whatever happened to those?