The evolution of GPT can be traced to 1986, when the General Electric Company (GEC) attempted a takeover of Plessey, a British-based international electronics, defence and telecommunications company founded in 1917; the takeover was barred by regulatory authorities.
[1] GPT was a world leader in many fields, for example Synchronous Digital Hierarchy (SDH) technology, and the merger brought the two companies responsible for developing and building the System X telephone exchange together, which was supposed to make selling System X simpler.
While most of Plessey's assets were divided between the companies, GPT remained a joint venture with a 60/40 shareholding by GEC and Siemens respectively.
In 1991, because Plessey no longer existed, GEC Plessey Telecommunications was renamed to just the initial letters GPT[1] (or GPTel in France, since in French "GPT" sounds like "j'ai pété", "I have broken wind").
In August 1998, GEC acquired Siemens' 40% stake in GPT (by now only existing as a legal entity) and merged GPT with the telecoms units of its other subsidiaries – Marconi SpA, GEC Hong Kong and ATC South Africa – to form Marconi Communications.