Copies of rare images of a First World War trench raid in progress form the centrepiece of a new exhibition.

The photographs, taken by a Royal Flying Corps warplane, show the September 1917 raid by soldiers on a German trench at Chérisy, in northern France. They are the only known images of a trench raid taking place.

Enlarged copies of the pictures feature in ‘All of a sudden, hell broke loose – the trench raid at Chérisy, 15 September 1917’ at Durham County Record Office.

Trench raids were commonplace on the Western Front during the First World War. They were undertaken to acquire prisoners and gather intelligence but, above all, to kill as many enemy soldiers as could be found.

Most raids occurred under cover of night and involved few men. However, the raid at Chérisy involved significantly more soldiers than usual, with the bulk being members of 9th Battalion DLI.

Military researcher Steve Shannon, who curated the exhibition, said: “The raid is largely forgotten today, submerged beneath the horrors of the Somme and Passchendale but it is unique, not only because of the number of soldiers involved but because the photographs showing it in progress are so rare.

“The raid also had an important outcome as it is believed that Lt Col Roland Bradford, from Witton Park, in County Durham, received a promotion to become the youngest general in the British Army, as a result of his involvement.”

For two weeks before the raid, Col Bradford trained the men of 9th Battalion DLI hard, even practising attacks on a full scale model of the target trench, until every raider knew what he had to do.

Less than a month after the raid, Bradford was promoted to brigadier general. Sadly, just a few weeks later on 30 November, 1917, the 25-year-old was killed by a German shell.

The exhibition at the record office, which is based in County Hall, also includes copies of original maps, documents and photographs from the DLI’s archive, which is cared for by Durham County Record Office on behalf of the Trustees of the DLI Collection.

The exhibition is free and is open Monday to Friday from 9am to 4pm until mid-2018.