The secret British spy base is part of a programme codenamed “CIRCUIT” and also referred to as Overseas Processing Centre 1 (OPC-1). It is located at Seeb, on the northern coast of Oman, where it taps in to various undersea cables passing through the Strait of Hormuz into the Persian/Arabian Gulf. Seeb is one of a three site GCHQ network in Oman, at locations codenamed “TIMPANI”, “GUITAR” and “CLARINET”. TIMPANI, near the Strait of Hormuz, can monitor Iraqi communications. CLARINET, in the south of Oman, is strategically close to Yemen.
British national telco BT, referred to within GCHQ and the American NSA under the ultra-classified codename “REMEDY”, and Vodafone Cable (which owns the former Cable & Wireless company, aka “GERONTIC”) are the two top earners of secret GCHQ payments running into tens of millions of pounds annually.
Those telcos basically work as subcontractors for the spies, helping them tap cables around the world and running the secure networks they use to listen in on all our conversations. They've helped GCHQ hack into cables run by other companies, including some on UK soil. They're collaborators in a global crime, and they deserve to be treated as such.