Art on front of house in Cheltenham shows three men huddled round a pay phone . Clad in trench coats and dark sunglasses , they hold old - fashioned listening devices . Some leaked documents also make a reference to GCHQ , although the UK government says the listening agency operates only within a strict framework of controls . The cover art has been widely attributed to graffiti artist Banksy . Britain 's GCHQ , the equivalent of the U.S. National Security Agency , is based in Cheltenham .
Art on front of house in Cheltenham shows three men huddled round a pay phone . Clad in trench coats and dark sunglasses , they hold old - fashioned listening devices . The cover art has been widely attributed to graffiti artist Banksy . Britain 's GCHQ , the equivalent of the U.S. National Security Agency , is based in Cheltenham .