Equinor’s outgoing UK upstream boss has declared it is “payback time” on the delayed $7.7 billion Mariner heavy oil development, which finally came on stream this month.

Mariner is the largest investment in the UK North Sea in the last decade but arriving at first oil has not been a smooth path.

Start-up is about two years behind the original schedule, set when the project was sanctioned in 2012 in a world of $100 oil.

The final price tag is about 10% above initial forecasts.