Ok visited this post here after having a mooch around Richmond Castle.
It took me about 15mins to get the hatch open as the hinges have snapped and it is hanging on by just the counterweight, but something was jammed making it only open so far. Eventually the lid popped open, and on looking down it didnt fill me with much hope. I took a few photos from down the shaft as i wasnt going to go down as i was only wearing flip flops, but then decided i would, getting god knows only what all over my feet. It had quite a lot on but everything was ruined.
Theres an interesting covered Resovoir over the road that looks like a Semi Sunken ROC HQ!!
Cheers Guys