Been offered a position, but it’s not my first choice?

I applied at two prisons and I’m genuinely happy to work at either but one will be a lot less stressful travel wise to get to, I applied for the second option as it is manageable travel wise and to hedge my bets a little bit on the chance I don’t get an offer at the first choice prison for months and months which obviously does happen

Unsurprisingly it’s the second choice that has got back to me within 2.5 weeks of passing the OAC and offered me a position

Here’s the question…

If I was to accept this offer and began the vetting, medical etc would that void the application at the first choice prison or would I be able to accept the offer at the first choice place and rescind this one?

And would it be frowned upon?

I’m happy to take this job and crack on but what with it only being 2.5 weeks since the OAC obviously there’s a good chance I would get offered a position at the first choice place yet and if that was to happen I would obviously want to go with the first one and have an easier time of travelling

Cheers guys