I got a noisy chimney - PLEASE HELP!!!

[daddym]

I have an average 1930s semi.
When it is even just slightly breezy, there is a repetative tapping / pinging sound in the chimney breast (upstairs).

It is definitely not dripping water - sounds almost like a metal ruler twanging against brickwork and picks up pace in line with the wind outside.

It is driving us mad at night!!!

Does anyone have any idea what it might be?

There are no caps on the chimney pots - this will be done as soon as the weather improves!

Thanks in advance!

 

[noseall]

metal flue liner

 

[daddym]

Thanks but what if there isn't one fitted? Or do you mean we should fit one?

There was an electric fire when we moved in, and when we put the living flame gas fire in, the Corgi installer checked the chimney and said it was all original and clean.