Secret Bunker?

 I have often wondered what this is. Is it an old railway turntable from days past when  perhaps goods trucks came up a branch line from the station not far away?  I posted the photo on that reliable source of local knowledge, the Tonbridge Daily Facebook Community Page and have had rafts of answers. Some think it is a secret bunker but most tell me it was a turntable for the delivery lorries in the 1960s.  One respondent tells me he used to play on it as a lad and I have sent him off to find old photos.  What a disappointment its not for railway carriages and it only dates back to the 60s. I am wondering why it has not been tarmacked over, it does not look like its turned in a while.