There is a whole rabbit warren of mines (and that's how the local cave rescue people describe it!) in the J7 area, and indeed littering the whole local landscape. An experienced local structural engineer once told me of many different issues he'd seen with building works in the area as a result, including near collapses around the Reigate area, and in fact reckoned you could get from Reigate to Godstone without heading above ground, though it would in practice probably involve very specialist equipment to ensure you survived!
Bedlam's Bank is situated near the M25 J7 area and is also near the approximate area once served by the sidings mentioned in this thread. It is the name of the patch of ground above a very complex series of mines and passageways. As a public word of warning, under no circumstances should anyone but the highly experienced and qualified attempt to enter such workings. You will only end up being rescued (dead or alive, quite possibly dead) if you don't know what you're doing round there. But some of these mines have proved very useful. I believe some materials for M25 construction were stored in them, and of course the resources have helped traders thrive over the years. We also recently discussed the Reigate Silver Sand Siding, which was between Redhill and Reigate on the North side of the line. (This infrastructure is now covered over by housing and also a locally-listed old factory and power plant, which can be seen from Madeira Walk. There is also paving with built-in tram tracks visible from said road.) Quite a few of these mines and pits were operated by individual, enterprising local traders. In the case of the Greystone quarries mentioned "upthread", it seems the history is very interesting and perhaps not all that well-known amongst locals.
