Battery Isolation switch ?

[TeGriffic]

I’ve just got a 4.3 1992 Griff and in the passenger footwell is a red plastic key with a small lug on it. It is, I am told, a battery isolation switch. Now, the arrangement looks, by way of the rubber cover, as though the key is not designed to be left there and thus, I thought I’d remove it. I think I have now momentarily isolated the battery. Interestingly, the car now idles incorrectly (see my post “Revs won’t drop”).

Presumably, by doing this, I have reset all sorts of things ?
Would that be a correct assumption ?