In reply to EddInaBox:
> (In reply to BigBrother)
>
> The small hole you have discovered is the ancient equivalent of the glory hole found in modern toilet cubicles, designed to allow the priest access to the young choirboys without breaking cover.
...lol, Genius - though perhaps oversized?
I think it's actually the chimney sweeps equivalent of a rodding point. I.e. access point to sweep the chimney from IMHO.