It's a personal choice, but I would never record an "official" meeting in secret simply because I wouldn't like that done to me. Also, if things do go to court then being above board at all times (in legal theory, at least) contributes to demonstrating my actions were open and honourable.
Of course, if the official refuses to continue I first try to persuade them with all the usual arguments (you're a public servant, there's nothing illegal to be discussed, it's perfectly legal, I promise confidentiality (with caveats), is it in the interests of the public purse/your shareholder's bottom line to waste time and money rescheduling?, and so on,) - in short, I do my best to hold the meeting.
If they still refuse, then fine. I ask for a written explanation as to why they are cancelling the meeting, smile, and bid them good day.
(I'd have no qualms making secret recordings of criminal activity, however - but that's a whole other can of worms...)
I haven't done this for a while now because I've dropped out of it all a bit, but it was fun. The thing to remember, though, is that they cheat. When their logical fallacies fail you get directed upstairs, where logic means nothing and force rules. Although it was enjoyable and empowering, it was also very stressful. To be frank, I'm far, far happier out of it - though it was a long, hard road from there to here. I have far less stuff and nonsense in my life now but more... I dunno', just more life, I guess.
Anyhoo, point is - they cheat. When they do, keep an eye on it - because unless you want to travel a tough and lonely road, you've got to know when to quit - or not.
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Tordels, I've dug that you-know-what out and I'll do the necessary when I get paid.