What would cause mould in this pattern?

[kpmatthews]

Hi
Any idea what would cause mould in this pattern? Perfect rectangular strips - the top seems to meet the damp proof course but i don't get why the straight sides and regular pattern all along the wall...

edit: just the black square-looking/rectangular bits... that darker brown strip across the length of the wall is just shadow



Thanks, Kristian

 

[PrenticeBoyofDerry]

Furniture or other obstructions against the wall!

 

[CambridgeBrummie]

Possibly previously wallpapered (and not very well), allowing moisture to be retained between the wallpaper and the plastered wall may have caused this patterning. Difficult to tell. Try scraping back the plaster slightly to see it is not coming from the other side of the wall.