A World War I training trench on Cannock Chase in Staffordshire has been preserved for its national importance.
It is believed the trench was used to train troops during WWI
The government has designated the site an ancient monument due to its significance in military history.
The exact location of the trench is being kept secret. It is believed to have been used by troops based at a training camp on the Chase in WWI.
The Forestry Commission, which owns the land, is to work with English Heritage to maintain the earthwork.
The trench was discovered 10 years ago by Forestry Commission worker Roger Wilson, who literally fell in to it while felling trees in the area.
'Important to country'
Cannock Chase was the location of a large training camp during World War I, which was used by up to 250,000 Allied troops.
"I sensed it was some sort of trench as soon as I saw it but I didn't know it was quite so significant," said Mr Wilson.
"The fact that it has been given scheduled status shows just how important this site is to the country."
The Department of Culture, Media and Sport issued the ancient monument designation.
Officials are not revealing the exact location to prevent vandalism.