Cable & Wireless plc was a British telecommunications company. In the mid-1980s, it became the first company in the UK to offer an alternative telephone service to British Telecom. The company later offered cable TV to its customers, but it sold its cable assets to NTL in 2000. It remained a significant player in the UK telecoms market and in certain overseas markets, especially in the former British colonies of the Caribbean, where it was formerly the monopoly incumbent. It was also the main supplier of communication in the British South Atlantic, including Saint Helena and the Falkland Islands. It was listed on the London Stock Exchange and was a constituent of the FTSE 100 Index.

Mercury Communications was a national telephone company in the United Kingdom, formed in 1981 as a subsidiary of Cable & Wireless, to challenge the then-monopoly of British Telecom (BT). Although it proved only moderately successful at challenging BT's dominance, it led the way for new communication companies to attempt the same.