Gas is coming ashore from one of the first wells to be drilled in a newly discovered field off the Norfolk coast.
The Arthur Field is 30 miles east of the North Sea gas terminal at Bacton and was discovered in October 2003.
The production platform stands in 140ft of water and output will be 110m cubic feet a day - enough to supply more than 200,000 households.
Operators ExxonMobil International used existing pipelines and networks to bring gas ashore in just over a year.
Chairman Robert Olsen said development would continue with the drilling of three more exploratory wells.
However, the operator warns that future output from the Arthur Field - with a potential of 130bn cubic feet - will depend on the market price for energy.
The field's potential means that at current production levels it will be able to supply gas for over three and a half years.