By last week, the evidence of a new and sustained attack against a crucial part of Russia’s economy was impossible to ignore. On Wednesday, a drone hit the Tuapse oil refinery in southern Russia on the Black Sea. Flames from the burning refinery were visible above an inky skyline. Nearby, the airport in Sochi – Putin’s favourite resort, famed for its pebble beaches – was forced to close.

So far this year, Ukrainian drones have struck at least four Russian oil and gas terminals across the country. The attacks are part of a growing asymmetrical campaign by Kyiv to cripple the industry and to deprive Moscow of the billions of dollars in global revenue it uses to fund its war. About half of Russia’s $420bn export earnings last year came from oil.