Given a leader with an iffy knee, the planned hike wasn’t going to work, and we had a rethink. We challenged ourselves to the rolling rock, a kind of continuous climbing wall that moves down as fast as you climb up, and then tips to simulate an over-hang. Kanchenjunga here we come! What comes up must come down, so we then explored the underground tunnel system – the nearest thing to real caving in Hertfordshire.