Derek Brockway kicks off the new series in Gwynedd with a 10-mile walk, that starts and ends in Penryndeudreath near Porthmadog and follows part of the Ffestiniog Railway line. He learns about the industrialist who changed the landscape and takes shelter from the rain in a farmhouse kitchen before exploring a Celtic rainforest. Meanwhile, Dr Jeni Millard visits a slate quarry now used to mature cheese and Onkar Singh Purewal discovers the story of the first recorded black person in north Wales