Wall covering identification help

[paramillitaryblobby]

Moved into a flat and I need some help identifying what's on my walls please.
Is this white cracked looking stuff wallpaper or is it painted lining paper? In some areas there are pencil markings to identify stud positions and at the corners there's a strip of plasterer's caulk on top of it... Could it possibly be the outer surface of the plasterboard?
It's universally cracked across the whole surface of the wall. It feels plasticey with a papery back. It was under a couple of layers of wallpaper. It is removable with a wallpaper steamer but it's a lot harder than the previous layers.
Thanks!

 

[opps]

I have never seen wallpaper that has a mud crack effect. Mud cracking can however be the result of the paint having been applied too thickly. I suspect that it was a vinyl wallpaper that someone painted over rather than lining paper.

A paper perforator will help the steam get through the paper much faster.

https://www.screwfix.com/p/zinsser-paper-tiger-scoring-tool-3mm/3469h

You run it over the surface and it makes tiny holes in the paper without damaging the plaster. Cheaper versions are available.

Edit, looking at image number one, it does indeed look like vinyl paper with a peel off surface that leaves the backing paper behind. If it is then I would recommend soaking the backing paper with warm soapy water to remove it, it is often faster and more pleasant that using a steam stripper.

 

[sparkwright]

Are you certain it's not a layer of paint, that's possibly reacted with paste, that's peeling off??