Damp patch mid-wall

[Phoenixfc7]

Hi

This is my friends house. She moved in a year ago and the patch was there then but was much smaller and not as wet. It's on a wall with a chimney and it is both sides of chimney and some evidence on same wall in back room. The wall is a dividing wall with another house. The house is a mid terraced. I think it's to do with the chimney/fire bathe fire is open bit she has never used it but it loos used previously. I think it's something to do with the real fire but I have no clue how to fix it, any help welcomed. Thanks

 

[Alastairreid]

Get the flue swept and checked then light a fire and get some heat up the flue, the damp wont be long in disappearing.