• bit late to the party, but in the Highway code excerpt
    "You MUST NOT use your horn",
    "except when another road user poses a danger" refers only to the previous two proscriptions:
    "while stationary on the road" and
    "when driving in a built-up area between the hours of 11.30 pm and 7.00 am"

    It does not ban you from using your horn whilst moving, and outside of those hours, for the purpose of "letting other road users know you are there".

About

Avatar for bq @bq started