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"This study cannot determine causality — for example, whether screen use causes insomnia or if students with insomnia use screens more," said Dr Hjetland.

“Of course, those who are healthy find it easier to work, raising their income. So it is not obvious which way the causality runs.”

Surrey Fire and Rescue Service said it attended the incident along with Kent Fire and Rescue Service and there were no causalities.

Police point to a drop in road causalities and crashes to suggest Wales' flagship policy is working, although a recent poll said seven in ten people still oppose the new limit.

But sometimes the causality goes in the other direction.