Plot: Dressed in the colours of the Welsh flag and with his 'new' Edwardian Bradshaw's guide in hand, Michael Portillo embarks on a railway adventure, from the coalfields of south Wales around the Bristol Channel to the southernmost tip of Cornwall. His first stop is Whitland in Carmarthenshire, where in the early 20th century, thrill-seekers gathered on Pendine Sands to indulge their need for speed