Hi, can anyone confirm whether the black stuff in the photos is mould? I think it may be mould but perhaps covered in dust, so I’m not sure. The photos are from an old disused fireplace that is now simply a hole in my bedroom wall with a breeze coming through it. I’m on the top floor with two flats under me but not sure if they have disused fireplaces connected to the same chimney (I’m in London, so they’re not in use anyway). Thanks very much for any advice.