Michael Portillo embarks on a railway journey around the ragged rocks of the western coast of Wales. He begins on the Victorian Cliff Railway at Aberystwyth, rising above the historic town to take in views over Cardigan Bay, home to the largest population of bottlenose dolphins in Europe.

On the beach at Borth, Michael discovers a petrified forest, part of a lost realm which was much mythologised in Wales during the Middle Ages. In Machynlleth in Powys, Michael visits the site of Wales's medieval national parliament and the charismatic hero who nearly achieved Welsh independence from England in the early 15th century.

Back on the coast in the seaside resort of Tywyn, Michael finishes this leg of his journey with a glorious ride aboard the first preserved heritage railway in the world, the Talyllyn, from Tywyn to Abergynolwyn.

Michael Portillo steams through the glorious scenery of the Snowdonia National Park on one of Britain's greatest heritage lines, the Welsh Highland Railway. Stopping off at Beddgelert, Michael takes in the awesome geology, which inspired Charles Darwin.

Back aboard the Welsh Highland Railway, Michael heads for Caernarfon, in whose 13th-century castle King Charles III was invested as Prince of Wales in 1969. Michael heads for the coast, where the Menai Strait separates mainland Wales from Ynys Môn, or Anglesey, to find the heart of the United Kingdom's mussel industry.

Continuing along the Menai Strait, Michael reaches its earliest road crossing, an elegant suspension bridge designed by the Scottish engineer Thomas Telford and opened in 1826. And from Bangor, Michael takes the train across the Britannia Bridge to the first station on Anglesey, known as LlanfairPG, to visit the island's sea zoo.