A vast battlefield landscape of tunnels and trenches dug to train troops for the first world war has been discovered on army land being cleared for housing.

Archaeologists who worked on the site at Larkhill, in Wiltshire, said the century-old complex was a valuable discovery – although it posed hazards.

“This is the first time anywhere in the world that archaeologists have had the chance to examine, excavate and record such an enormous expanse of first world war training ground,” said Si Cleggett, of Wessex Archaeology. “These men were being trained for the real thing, using live grenades – we know that because we found over 200 grenades in the tunnel and 50% of them proved to be still live. We had to work side by side with experts in dealing with live ordnance, or it could have got very tricky.”

The site is full of evidence of the soldiers who trained there. Graffiti still covers many of the tunnel walls, and some of it has been matched to service records, including those of Yorkshire coalminers, two brothers who signed their name “Halls” with the motto “Semper Fidelis”, and one man who later deserted.



The names also included L/Cpl Laurence Carthage Weathers, a New Zealander who in September 1918 would draw on his training as he charged the German frontline in France under machine gun fire, lobbing grenades into their trenches, returning twice to his own lines for more grenades, and knocking out three German machine gun posts and taking 180 prisoners. He died in an ambush a month later, without learning he had earned a Victoria Cross for his efforts.



“This wasn’t a couple of hours and back to barracks to a warm bed operation; the men were down in these tunnels for weeks on end, and all through the brutal winter of 1916-17,” Cleggett said.



Finds at Larkhill, Photograph: Cundall and Aerial-Cam Ltd

The recruits left mess tins, combs, toothbrushes, cigarette and tobacco tins and pipes, candlesticks and candle stubs, tins of condensed milk and meat paste, a jar of Canadian cheese and a tin of Australian toffees, as well as scorch marks from their cooking fires and candles. A bucket was found that had been adapted into a brazier to help combat the bitter cold at night.



The men being trained to fight on and under the battlefields of France and Belgium couldn’t have known that their tunnels ran through millennia of earlier history. The site is two miles from Stonehenge, and the excavation also uncovered a wealth of prehistoric material, concentrated around the dry valley through which the river Avon once flowed. The discoveries included an enclosure older than Stonehenge, a small henge monument, Iron Age round huts lived in at the time of the Roman invasion, and a miniature pottery beaker found with the bones of three children buried 4,000 years ago.

Although no detailed plans survived of the tunnels and trenches, some people certainly knew of them after the war: among the most intriguing later finds were a 1950s motorbike and a 1930s red MG sports car. Andy Corcoran, the project manager, said the site workers knew that news of the tunnels would still prove a magnet to the more adventurous local spirits, and so each day’s work was sealed with metal plates and blocked with tonnes of chalk, which all had to be dug out again the next morning.



A century ago, the casualties began even before the men reached the front. Among the Australians trained at Larkhill, many of them farm boys and labourers who had never before left home, some arrived with flu or chest infections caught on the gruelling journey, and 141 died in training – 80% of them of broncho-pneumonia, and one of asthma.



The archaeologists believe the training land began with the trenches, and then the tunnels were added from 1915 as the nature of the war and the fact that it would certainly not be over by Christmas became clear. In places the tunnels are several levels deep, cut up to 6 metres below the surface.

The men were trained to dig listening posts and sit, stethoscopes to the wall, listening for enemy activity, and then dig deeper tunnels to run under the enemy posts. Some of the men who fought at the battle of the Somme in 1916, which began with mines being detonated in deep tunnels, and the Battle of Messines, which began in June 1917 with 19 mines being set off under German trenches, were trained at Larkhill.

The tunnels were found as work began on the army land to prepare a site for 400 new houses for service personnel and their families – part of a £1.1bn project to accommodate an extra 4,000 extra service personnel in and around Salisbury Plain by 2019. The tunnels will be permanently sealed and pumped full of a slurry made from the excavated chalk before construction work begins.

Although nothing could have adequately prepared the men for the horrors they would face on the frontline, training trenches and tunnels were built at many sites around the country, most of which have since been destroyed by development. Analysis three years ago of aerial photographs taken half a century earlier revealed an entire mock battlefield that had vanished under scrub and bracken on land still owned by the MoD at Gosport, in Hampshire.



At Larkhill, the archaeologists wonder whether some mutiny in the ranks lay behind what must have been the baffling overnight disappearance of the 1930s sports car, the kind that might have been driven by some flashy young officer. It was driven into a deep trench, and chalk was shovelled in to cover it. It has now been carefully logged and stored alongside the meat tins and the Roman pottery, but is in need of more conservation work than either.



“To advertise the car as one careful owner in need of some TLC would undoubtedly be pushing it,” Cleggett said.

