Production has begun at a new offshore gas plant will bring the vast reserves west of Shetland to the mainland.
The new Shetland Gas Plant is said by operator Total to be capable of supplying energy to two million homes.
A flare was lit at the moment gas started flowing to the plant from the Laggan and Tormore fields, 125km north west of Shetland.
The gas plant is said to have been the biggest construction project in the UK since the London Olympics.
Almost one fifth of the UK's remaining oil and gas reserves are thought to lie in the area to the west of Shetland.
Total said the Laggan and Tormore fields will produce 90,000 barrels of oil equivalent per day, which will be piped back to the gas plant which lies just to the east of the existing Sullom Voe Terminal.
From Shetland, a pipeline takes the gas back to the UK mainland and into the national gas grid.
It is expected to provide about 8% of the UK's gas needs, supplying more than two million homes.
The project is part of a massive £3.5bn investment by French company Total. Challenging weather conditions delayed the project by more than a year and added millions to its cost.