AN intriguing relic of the First World War is recalled tonight in the opening programme of a remarkable documentary series.

Trenches dug across Belhaven Bay, 30 miles east of Edinburgh, are glimpsed in Scotland from the Sky. Presenter James Crawford traces the remains of the trenches, which he describes as “snaking away through the long grass”. When seen from above, he adds, their “tooth-like outline … is remarkably clear.”

Alan Kilpatrick, who has studied the history of the trenches, tells Crawford as they stroll along the beach: “This is defined by the British as a site where invasion could happen, so it has to be defended, and you defend it by digging trenches.” A hundred years ago, Kilpatrick adds, along the edge of the beach, at the high-water mark, there would have been barbed wire and machine-gun posts, with a communication trench at the rear. Some 700 metres of trench system survive at Belhaven Bay today.

The three-part series explores Scotland’s cities, coasts and countryside from the air and uses a century of aerial photography to show how rural and urban landscapes have changed. It features rare material from Scotland’s National Collection of Aerial Photography, which is managed by Historic Environment Scotland, where Crawford works. He has spent a decade researching, and writing about, the history of the archive.

In the second programme next week, Crawford will show how, in the years after the Second World War, planners and architects took to the skies to re-design towns and cities across the Central Belt.

* Scotland from the Sky, BBC One Scotland, 9pm. An accompanying book (Historic Environment Scotland, £25) is now available.