"We're more confident than ever we can win," said environmental lawyer Tessa Khan before the case opened at the Court of Session in Edinburgh.

Her optimism was shared by hundreds of people who demonstrated outside the court off the city's Royal Mile, given recent rulings that have put the future of the fields in doubt.

Campaign groups Uplift and Greenpeace argue that the UK government granted permissions unlawfully by failing to take into account all emissions from burning oil and gas.

A win for the campaigners would mean operators would have to resubmit environmental assessments for approval before drilling can start.

Former Scottish National Party lawmaker Tommy Shepherd said the case's impact will be felt across the sector.

"This is the granddaddy because it is so big, but the case will be applied to the decision-making process in general," he told AFP.

"There were 100 licences granted by the last Conservative government in its final dying months. All of them will now be under question."

Regulatory approval for drilling at the Rosebank oil field, 145 kilometres (90 miles) off the Shetland Islands in Scotland's far north, was granted last year.

It is the UK's largest untapped oil field, estimated to contain up to 300 million barrels. Drilling had been due to begin between 2026 and 2030.

The Jackdaw gas condensate field, approved in 2022, is being developed 155 miles east of the Scottish city of Aberdeen and was expected to start production next year.

Rosebank is owned by Norwegian energy giant Equinor and the UK's Ithaca Energy. Jackdaw is owned by Shell.

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Equinor

Ithaca Energy

Shell