Richard Dixon, director of WWF Scotland, said the news the leak had stopped was welcome, but pointed out it was the second serious leak in the North Sea in two years.
"We should be trying to give up our addiction to oil and gas, and not seeking it out in more difficult places with the risks to the environment that poses when things go wrong," he said
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The country's counter-terrorism forces have regained control of the facility.
The commissioner of the Metropolitan Police has said he cannot promise the public an attack will not take place.
The showers are likely to be particularly heavy across northern parts of the country.