Chimney Damp in Attic 3ft Down on Chimney Breast but no Obvious Leaks?

[ROSEVILLE]

Good morning all.
We have a house built in 1922, it has solid 15in brick walls, we have lives here for 30 years and have had little problem.
About 12 months ago we had damp down the wall in the bedroom, it was identified as failed flashing. This has not stopped the damp and seems to be getting worse. The attic is very large and the slates are sprayed with foam!!, there are two roof vents across from each other. The damp seems to be starting about 3 feet down the chimney stack where it starts to bow, there does not seem to be any leaks from the roof, all other walls are dust dry. Does anyone have any ideas before we spend a fortune on scaffold.
Thank you all in advance.

[welsh brickie]

is there an airbrick in the breasting, if not there should be, moisture builds up in the flue causing damp,

[ROSEVILLE]

Sorry forgot to say that the chimney is vented at the top with a pepper pot type top and bottom with a vent.
Please what is a breasting.
Thank you.

[welsh brickie]

the chimney breast is the wall that surrounds the flue, each floor must have a air vent if the fireplace is blocked up this is to stop condensation forming in the flue causing damp,

[michaelscad]

check your chimney it sould have a cowl on it t stop the rain getting in