It's our final BMW touring experience so we're going back to our roots. Apparently, most people in the UK can trace their ancestry back to the Mendip Hills in Somerset and, more specifically, Cheddar Gorge. Underground, once you've passed the remains of Cheddar Man in the enchanting surroundings of Gough's Cave, it's time to go off-piste and explore the intricate and exhilarating system of underground tunnels and caverns. Cheddar Caves and Gorge is the only place in the UK where you can literally turn up and try your hand at potholing, so we sent our reporter Kylie Norman to take a step into the darkness and back in time. For more information, go to the Times Your World website