Newnham Church

This is the main entrance to Newnham Church here in Northamptonshire.
No longer in use I?m told because of safety reasons and access.
The side door has been used to gain access for quite a few years now, well before we moved here.
But I have often wondered what the small door on the right was used for.
None of the locals seem to know other than joking about keeping naughty children in there.
I bet one of you will know!
Answers on a postcard please ;-)