What on earth is this and how fix?

[littleFinch]

Moving into new house tomorrow, dropped off some fragile things today and noticed this issue with the chimney breast. We've had a rewire this week but I couldn't say that this was here before that work or not.

It's basically a hole in the side of the chimney breast, filled with some expanding foam. They didn't do any work this side and all of their fixing has been plaster or polyfilla.

So it is likely to have been here from last people - how do we get this fixed?

Filler it, sand it flush and then paint it.

Is it on the ground floor, or is there another fireplace beneath it?

Is the fireplace permanently out of use?

Maybe they previously had a gas fire there and the hole is where the pipe was? I'd just fill it.

@PigletJohn ground floor and permanently out of use.

There is a crappy cover where the fireplace used to be so I don't think anything has been done to update it/make use of the space.

"ground floor and permanently out of use"

In that case you can fill it without fear of fumes leaking into the room. It is odd.

One guess is that there used to be a socket or switch for an electric fire that has been removed. The old cable might have been in the fireplace cavity behind the hole.