Coast travels right around the wonderful Welsh coast from the Severn estuary, to the Dee estuary. Nick Crane investigates the evidence that a devastating tsunami crashed on to the coast of Wales and England some 400 years ago. Villages were wiped off the map and thousands died, leaving the survivors to believe they had suffered the judgement of God; but was it a tidal wave that was to blame? Nick also discovers why scientists planning an expedition to the Red Planet find the Welsh coast a surprisingly good stand-in for the surface of Mars. Alice Roberts attempts to get airborne with just helium balloons attached to her waist as she tests the claim that the world's first powered flight was actually made by a Welsh carpenter. Meanwhile, Miranda Krestovnikoff lands where few people ever tread - on Grassholm; an extraordinary island normally kept exclusively for the birds. In 1947 two brothers were on holiday on Anglesey when one sketched a rough notion in the sand for a completely new kind of vehicle - Dick Strawbridge explores how that coastal blueprint became the plan for the Land Rover. Plus Tessa Dunlop reveals how some 30 years ago an army of local volunteers managed to keep 3,000 Asians, who had been expelled from Uganda, warm and well-fed in an abandoned military base during a Welsh seaside winter.

• Alice Roberts
• Miranda Krestovnikoff