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I’ve reuploaded it. If not better I’ll take one later.
The wall condition isn’t best but plaster hasn’t blown. It was lined and wallpaper previously. I’ve just painted it white for the time being.
musa-
It's better. I would try to get some plasterboard on the underlying wood. Maybe cut out a regular shape first and screw the plaster board to the joist. Then it would depend on movement in the surrounding area, if the rest of the plaster is solid up to the joist just skim the plasterboard, maybe use some jointing scrim on the edges. I would recommend lining on top of that though.
Apologies if I making it sound like a piece of plasterboard would be the easiest thing to get hold of these days. You might find some small abandoned pieces outside building sites or in a skip.
Airhead
The picture resolution is very low, I know this site is tricky to post pictures on though!
It looks like a good candidate for lining paper, especially if the ceiling is moving a lot. At least plasterers scrim or the flexible Toupret with their fine scrim over the crack, feathered out into the rest of the ceiling with tx110.
Can't really see the condition of the wall from the photo.