At the centre of the infrastructure was the central control room of the National Grid. The engineers who worked there had information about the running costs and availability of every power producing plant in England and Wales. Here they would constantly anticipate demand, monitor and instruct power station managers to produce electricity, or stop producing electricity, by reference to what was known as the "merit order". The objective was to ensure that output was always achieved at the lowest possible cost.
The electricity market in the UK was built upon the breakup of the CEGB into three generating companies and the National Grid Company. The three generating companies were Powergen, National Power and Nuclear Electric. The first two were privatised in the early 1990s and the latter was held in public ownership for several years before combining with Scottish Nuclear and privatised as British Energy.