Elfin Safety gone mad as usual. Seems they put a cage across the entrance to stop peeps hurting themselves in the dark dangerous cave. Then they decided there was a risk of people impailing themselves on the pointy bits when trying to climb over the top... so they took the locks off the cage door. Sigh.
Kind of gives a nice fantasy-esque 'Colossal Cave' type feel to the place though, so all's not totally lost.