All around me was dark. I think it has been kept that way – midday outside but a kind of gloaming inside – probably the closest a visitor can be made to feel what went on in these narrow corridors and dungeons. The wall plaster is peeling in most places and remains of corroded iron hooks from where chains were once clamped can be seen. Lanterns hung from low ceilings looking like cages purpose-built to make even light struggle to do its work.  An array of narrow chambers into which