Punkawallah
Veteran
Fair enough if they had booked the cyclist on that basis. But the police are using the UN convention as a basis, then it should be applied across the board.
Whether that particular law applies to bicycles is another thing. Somewhere in it will be a definition of the ‘vehicle’ it applies to, and possibly somewhere else will be guidance or clarification for that definition. Welcome to the British legal system :-) We have some 7,000 laws on the statute books, and ignorance is considered no excuse under the law.
As far as the UN Conventions go, they are aimed at governments and officials rather than citizens. If the police officer concerned is trying to arrest someone for a breach of human rights, I suspect their desk sergeant would have something to say about it.