Harpur Hill in Derbyshire was used as an artillery range in World War I when it was known as the Frith. In World War II, however, it become one of the UK’s largest ammunition stores as RAF Harpur Hill.
In the late 1930s, 11 tunnels were bored into the former quarry for ammunition storage and RAF Harpur Hill was established in 1939. The excvations are reported to have cost over 6 million pounds - a considerable sum. The seven largest tunnels extend for over half a mile and are 5 metres high and 7.5 metres in width. Railway lines are laid within the tunnels. The remaining four tunnels are at a lower level and are slightly smaller in profile. The tunnels lie up to 18 metres beneath ground level.
The RAF vacated the site in 1960 and the tunnels found re-use as a mushroom farm through to the mid 1970s. Subsequently the site was used for the storage of cheese and bonded stores. For a period Derbyshire College for Further Education was based on the site.
The Health and Safety Executive now has laboratories at Harpur Hill which were built in 2002. They use the extensive grounds for large scale testing of items such as tube trains and shipping containers. The laboratories developed from the original Safety in Mines Research Establishment - another underground connection.