Damp patch? just discovered a small wet patch at the top of a chimney...

just discovered a small wet patch at the top of a chimney breast in one of our bedrooms. What should i do
Answers:    In adjectives probability it is the flashing between the roof and the chimney stack that is at knock, you need to bring back it checked and replaced/refixed as soon as possible because if you are now getting chilly below the ceiling then that finances that the roof timber, the ceiling joists and ceiling stuff is now drenched.
Carefully climb into the attic and check out where the drizzling spot is coming from. Sounds as if you have a filter from pipes, condensation or even holes from roofing tacks. Check it out up to that time it gets to doomed to failure.