Sandy Haven to Milford Haven

At Sandy Haven the Coast Path stops being about Atlantic cliffs and becomes something stranger and, in its own way, just as interesting: a walk along one of the great deepwater harbours of the world. Nelson called the Milford Haven waterway one of the finest natural harbours he had seen, and the supertankers easing past the pilot boats make the point for him.

First, the tide. The crossing of the Sandy Haven pill is by stepping stones and is only there at all for a couple of hours either side of low water; get it wrong and the detour by road adds four miles of lanes. Every guidebook says plan around it, and every season somebody doesn't.

Beyond the pill the path runs through woods and field edges along the shore, and honesty requires saying what you will see: the jetties of the South Hook LNG terminal striding out into the water, tankers at their moorings, and the working plumbing of the energy industry that has kept this town alive since the oil era began in the 1960s. Some walkers write this stretch off; taken on its own terms — big ships, big water, big sky — it has a fascination the postcard coast can't offer.

Gelliswick Bay gives you a beach and the fort on its hill, and then the path arrives in Milford Haven proper: a planned town (laid out in the 1790s, with early input from whalers from Nantucket), a marina that has grown a waterfront of restaurants and a hotel, and the town museum in a former whale-oil warehouse telling the whole improbable story.