Whats causing damp and cracks?

[DIYinfo]

Can you tell me what is possibly causing damp and cracks in communal hallway, ceiling shown in image, roof is above the hallway ceiling. There is a window in the wall below the ceiling 3 to 4 ft lower than the ceiling, The window is kept continually open, even in winter. I dont have access to the loft and roof above.
I have enhanced the image to make it more visible.

Here is what it looks like in reality without photo enhancement exaggeration, and how it actually looks like in real life.
https:
Here are some others of the ceiling. enhanced picture.

this is what it actually looks like

There are also cracks in the corner of the wall, at the seam, edge.

[Notch1]

A picture from much further back and one from outside is needed to get any idea what is causing it.

Given that it is at ceiling level, a roof leak is favorite, but without knowing what the roof construction is, its impossible to tell.

The photo shows water has run onto the top of the plasterboard, then run across until it has got in at the corner.

Does it happen on rainy days?

Have you had any roof work done recently, loft or cavity insulation?

[DIYinfo]

The roof was repaired some years back, I cant remember what side it was, the owners of the leasehold will not allow me access to the roof, (I am the freeholder) so a solicitor is having to deal with them.
I have not noticed it getting worse, could this be old damage from the past? Or would it of dried out? Would you say this is ongoing?
I a not sure if any loft work, insulation etc has been done, as the leaseholders will not talk to me at all.

[Notch1]

The roof was repaired some years back, I cant remember what side it was, the owners of the leasehold will not allow me access to the roof, (I am the freeholder) so a solicitor is having to deal with them.
I have not noticed it getting worse, could this be old damage from the past? Or would it of dried out? Would you say this is ongoing?
I a not sure if any loft work, insulation etc has been done, as the leaseholders will not talk to me at all.

They dont sound very helpful

If can reach it, put some pencil marks around the perimeter of the staining, if it spreads you will know.

Next time you get a period of sustained heavy rain, see if its wet. Some leaks only occur in strong winds, so note the conditions.

Unfortunately, looking at the staining reveals nothing really, the outside and the loft is where the cause of the problem can be found.

[DIYinfo]

Thank you for the info.
If whatever is making the damp was fixed from the roof or loft. What kind of fix would need to be done from the inside on the ceiling and walls?