British Gas was formed from the infamous 'Tell Sid' privatisation of the British Gas Corporation in 1986 by Margaret Thatcher's government. Its parent company is Centrica, a UK-based multinational energy company that also supplies customers the US and Ireland and has interests in the exploration and production of natural gas. Centrica is a plc listed on the London Stock Exchange.
British Gas supplies electricity and gas to over twelve million homes in the United Kingdom, and is the biggest energy supplier in the country. It's part of the 'Big Six' energy companies that dominates the gas and electricity market in the United Kingdom.