It is interesting to note that the BBC changed its headline on that story. When it first appeared it was headed something like 'Prince says police 'wrong' to stop him'. I don't know whether the palace complained or someone at the BBC spotted it.
I have no way of knowing whether Andrew said it was 'wrong' because the system is supposed to work so that the patrolling officers are told if someone leaves the palace for a walk in the garden.
"Prince Andrew says the police do a good job and "sometimes get it wrong "
Yes, well so do Princes.
The Police are damned when they do, and damned when they don't. Were I a royal personage I think I would far rather that the Police failed safe on matters of security, and when something like this happened I would keep it between myself and the officers involved, rather than ensuring that it leaked, so I could graciously and publicly accept an apology that shouldn't have been necessary.
Prince Andrew is an insufferably pompous individual, and this incident highlights the fact.
FE - I'm not completely defending Prince Andrew in this instance, not least because I have seen at first hand him "forgetting" about the police. But we do not know the full circumstances or who leaked it.
I also wonder what evidence you have for stating that he is an insufferably pompous individual.