A quick update for @Moto_Hodder:
Not wishing to distract from getting the message about our new @SaferSE23 Twitter account out there, it seems red, circular road signs - like the one for no motorised vehicles - must be adhered to in order to stay within the law. That’s according to the RAC’s information about the Highway Code listed here: https://www.rac.co.uk/drive/advice/learning-to-drive/the-highway-code-uk-road-signs-and-meanings/
To quote: “Circular road signs: Circular signs give orders - they must be followed to stay within the law. Circles with a red border tell you what you must not do (i.e. take a U-turn). Blue circles usually give a positive instruction, such as ‘turn left ahead’.”
Of course prosecution is extremely unlikely, and it’s not the aim of @SaferSE23 either. What we hope to do is inspire the companies behind local delivery riders to take responsibility, and ensure their people use the roads more safely, in line with the signs.
[Edited to add: I’ve just looked at your profile and see you’re a lobbyist for the motorcycle industry so you must know all this already and actually I feel a bit silly for replying now! Ah well, it’d be great to have your input if you are also keen to help keep the roads around here a bit safer?]