How to deal with wet plasterboard?

[Keitai]

the issue is this damp wall and corner of the room. It is from external water penetrating through when it rains. Looking to do what we can to stop the water showing through
The external wall is solid brick - no cavity. The interior is plasterboarded by the feel of it. Probably needs taking off and starting again with a water resistant board or something? Let the water run down to the earth under the floor. We are lower ground (no one underneath) It's been getting worse for a few years now. Suspect the boards and the battens behind are wet

 

[opps]

I guess you need to stop the water ingress in the first place. Any remedial works inside are likely to fail. In time, once the leak has been dealt with, the plaster will dry out, but it might take weeks.

 

[Keitai]

I guess you need to stop the water ingress in the first place. Any remedial works inside are likely to fail. In time, once the leak has been dealt with, the plaster will dry out, but it might take weeks.

Apparently it's just rain coming through an old wall with no cavity!! So they say. What can you do about that?

 

[foxhole]

Who is “they”?
Lower ground = basement?

 

[Keitai]

Given up wanting to stop leak from outside. He just wants to rent out the flat. What's the bestvway to hide these water stains? Some sort of panelling on batons just to right of curtains? Or also going round corner a bit or just ending at corner

 

[Murdochcat]

Who is “he” and who are you ?

 

[HERTS P&D]

Well, I'm glad you are not doing bodge!

I have walked away from jobs where landlords want to cut corners, do the job correctly or find someone else.

Andy