Michael Portillo continues his railway journey in north Wales, tracking the coastline north from Harlech to skirt the Llyn Peninsula.Beginning on the shifting sands of Morfa Harlech, in one of the most important dune systems in Wales, Michael is surprised to find a team of conservationists felling and grubbing out trees. Next stop is Porthmadog, once one of the most important slate ports in the world, where slate was exported to South Africa and Australia.From the top of Cardigan Bay at Pwllheli, Michael heads for the South Caernarvonshire Yacht Club to lend a hand on deck of a classic wooden racing boat. Close to the tip of the Llyn Peninsula, Michael reaches Aberdaron, where St Hywyn's Church - the former church of Welsh poet and vicar RS Thomas - looks out over Aberdaron Bay.