The Doughnut is the nickname given to the headquarters of the Government Communications Headquarters (GCHQ), the British cryptography and intelligence agency. Now in its hundredth year, GCHQ is located on a 71-hectare (176-acre) site in Cheltenham, Gloucestershire, South West England and is the largest building constructed for secret intelligence operations outside the United States.
Beneath the central green roof a PermaQuik waterproofing system was specified to provide a lifetime of waterproofing security by Radmat Building Products.
