<P> BT Group is a holding company; the majority of its businesses and assets are held by its wholly owned subsidiary British Telecommunications plc . BT's businesses are operated under special government regulation by the British telecoms regulator Ofcom (formerly Oftel). BT has been found to have significant market power in some markets following market reviews by Ofcom . In these markets, BT is required to comply with additional obligations such as meeting reasonable requests to supply services and not to discriminate . </P> <P> BT runs the telephone exchanges, trunk network and local loop connections for the vast majority of British fixed - line telephones . Currently BT is responsible for approximately 28 million telephone lines in GB . Apart from KCOM Group, which serves Kingston upon Hull, BT is the only UK telecoms operator to have a Universal Service Obligation, (USO) which means it must provide a fixed telephone line to any address in the UK . It is also obliged to provide public call boxes . </P> <P> As well as continuing to provide service in those traditional areas in which BT has an obligation to provide services or is closely regulated, BT has expanded into more profitable products and services where there is less regulation . These are principally, broadband internet service and bespoke solutions in telecommunications and information technology . </P> <P> BT Group's world headquarters and registered office is the BT Centre, a 10 - storey office building at 81 Newgate Street in the City of London, opposite St. Paul's tube station . </P>

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