(Reuters) – The owners of London’s ExCel conference center on Friday won a court ruling against insurers, including Royal & Sun Alliance Insurance Ltd., over pandemic-related losses, which its lawyers said could affect hundreds of thousands of policyholders.

London International Exhibition Centre PLC took legal action at London’s High Court last year over business interruption losses caused by the COVID-19 pandemic, claiming £16 million ($20.5 million) under its insurance policy.

The test case, which also involved a similar lawsuit brought by restaurant chain Pizza Express, concerned “at the premises” clauses in various insurance policies and whether the closure of businesses was covered.

Judge Richard Jacobs ruled in a judgment published on Friday that the United Kingdom Supreme Court’s 2021 ruling on disease clauses in insurance policies – a case brought by Britain’s markets regulator, the Financial Conduct Authority – also applied to at the premises cover.

The judge said several at the premises claims brought by policyholders following the FCA case had been settled by insurers.

But business interruption cases that had gone to trial concerned either “radius” disease cover, relating to policies that cover instances of a disease within a specified radius, or some other insured peril, such as prevention of access. Judge Jacobs’s ruling found at the premises cover to be indistinguishable from radius cover.

Law firm Stewarts Law LLP, which represented the owners of the ExCel Centre, said the ruling “could potentially affect hundreds of thousands of policyholders.”

“Policyholders whose BI losses remain uncompensated should now revisit their policy documents to consider whether they may now have a valid claim to pursue,” the firm said in a statement.

RSA declined to comment. Allianz SE, which was also a defendant in the test case, said it was reviewing the ruling’s implications.

Becky Rogers, head of property claims at Allianz Commercial, said in a statement the company would need to consider its position given the judgment.

“In the meantime, (we) will be working through how it is likely to impact those of our policyholders who have outstanding COVID-19 business interruption claims under disease at the premises clauses,” she said.