Chatham and Clarendon School, not a sinkhole but what is it

As you can see from the picture the shape is an oblong with curved ends and the brickwork extends down about 2 metres.

I guess it must date from somewhere between 1800 and 1900 and was in the grounds of Townley House and Townley Castle when it was built, click here for a potted history of both http://www.michaelsbookshop.com/blogpicts2/townley.htm

The picture above is Townley castle built around 1800 it was on the Chatham House School site.

 I am pretty sure that this was a water well, but the shape is unusual, possibly that shape for a chain pump.

The water table there would be about 70 feet down so a suction pump wouldn't work.

This 1872 map shows the location of Townley Castle

and this map the sheet to the right or east of the previous one the red oval is roughly where the hole is.

Brick lining the top metre or so of a well is fairly normal practice.

I guess the nearest building was St George’s School so it could have been related to the water supply for that. I think Chatham House and St George’s School shared the playing fields

Looking at this map which I need to check the date of.  

I think Townley Castle may have been finished off WW1 bombing although the information from the time is a bit vague. 

I will add to this post as thoughts occur to me.