The first test of the prototype telephone occurred on 10th March 1876 when Scottish born Alexander Graham Bell said to his assistant on the phone: "Mr Watson, come here, I want you". Following the invention, the Telephone Company Ltd was formed in 1878 in the UK to sell telephones. This company was taken over by the Post Office in 1912, which then controlled almost the entire telephone network in the UK.
Telecommunications however really took off in the UK when Subscriber Trunk Dialling (STD) codes were first introduced in 1958 to allow callers to call another telephone directly without having to go through the operator, although this wasn't completed until 1979.
The Post Office was a government department with the Postmaster-General sitting in cabinet until 1969 when it became a public corporation (or nationalised industry) under the Labour government in 1969. This split the Post Office into two separate businesses –post and telecommunications.
In 1980, the telecommunications side of the Post Office was named British Telecom by the new Conservative government, and remained part of the Post Office until the following year, when it became a separate public corporation under the British Telecommunications Act 1981. The act allowed for competition in communications, and in 1982 Mercury Communications Ltd was created as the main competitor to British Telecoms. In 1983, British Telecoms and Mercury Communications were granted a 7 year duopoly on Britain's telecommunications, until 1991, when full competition was allowed. British Telecoms became a Public Limited Company (plc) in 1984, being sold off in large chunks until the final privatisation in 1993. Oftel (Office of Telecommunications) was created to regulate it, which was transferred to OFCOM (Office of Communications) in 2003. British Telecoms was renamed BT in 1991, and is now one of the largest communications companies in the world.