Thanks for feed back
Have checked and chimney is capped. Also not the only patch just the worst one.
Lastly cowboy due to the awful job every where, ruined sofas, ruined carpets, radiators left off walls and many many other issues.
Have had whole house replasted recently and turns out the guy was a cowboy. One of the problems we have been left with is damp patches on walls. Some patches appearing on interior walls and not by pipes so let’s assume it’s not caused from DPC or pipes etc.
The patch in the picture is the...