War is now a possibility in Norway, by the prime minister’s own admission. The country, which borders Russia, has gone into “total defence” mode, preparing its population for the worst in light of the fighting in Ukraine.

Dug beneath a peaceful park, the St. Hanshaugen air raid shelter, one of Oslo’s largest, can take in 1,100 people behind its heavy metal doors if ever the worst comes to pass.

The air is chilly, the lights dim, and the toilets basic: it is far from cosy, but it is designed to protect against the threat of bombings and chemical, biological, radiological and nuclear materials.

“Today we have about 18,600 shelters, [enough to protect] a little less than 50 per cent of the population” of 5.6 million people, the head of Norway’s Civil Defence Oistein Knudsen said.

“Quite a few of them need to be upgraded. They were built during the Cold War. They are humid. They’re old,” he said.

Nato member Norway wants to reinstate the obligation for new large buildings to be equipped with air raid shelters, a requirement lifted in 1998 after the collapse of the Soviet Union.