Gas is delivered to the seven reception points (called beach terminals) by gas producers operating Offshore Facilities from over 100 fields beneath the sea around the British Isles. In addition a newly commissioned terminal at the Isle of Grain allows Liquefied Natural Gas (LNG) to be delivered to the terminal by sea. After treatment, which includes checking the quality meets the safety requirements and measuring the calorific value (the amount of energy contained in the gas), it is transported through 275,000 Kilometres of iron, steel and polyethylene mains pipeline.

The National Transmission System (NTS) is the high pressure part of National Grid's transmission system and it consists of more than 6,600 Kilometres of top quality welded steel pipeline operating at pressures of up to 85 bar (85 times normal atmospheric pressure, over 1250 psi). The gas is pushed through the system using 26 strategically placed compressor stations. From over 140 off-take points, the NTS supplies gas to 40 power stations, a small number of large industrial consumers and the twelve Local Distribution Zones (LDZs) that contain pipes operating at lower pressure which eventually supply the consumer.

The twelve LDZs are managed within eight gas distribution networks. Following the sale by National Grid of four of the distribution networks, the owners of the distribution networks are now:

• North West, London, West Midlands and East of England (East Midlands LDZ & East Anglia LDZ) are owned and managed by National Grid (the area outlined in black)

• Scotland & South of England (South LDZ & South East LDZ) are owned and managed by Scotia Gas Networks – operating as Scotland Gas Networks and Southern Gas Networks respectively

• Wales and the West (Wales LDZ & South West LDZ) is owned and managed by Wales and West Utilities

• North of England (North LDZ & Yorkshire LDZ) is owned by Northern Gas Networks, who have contracted operational activities to United Utilities Operations