it's the whats been used.

Just been to view some old dears main wall in her bedroom and she asked me
could I solve the damp problem, which nearly covered the whole of the wall.

Black patches where showing through her pink coloured wallpaper(very
unsightly) anyway I asked her could I strip parts of the wallpaper of to
reveal what was happening.
Lo and behold some pillock she got in to do the wall originally some 5 to 6
years ago had knocked a large area of plaster out and used mortar to fill it
instead of plaster(what a plonker),needless to say he didn't inform her to
get her guttering replaced.