For now, Berlin can breathe a sigh of relief: after a ten-day shutdown for maintenance, the Nord Stream 1 pipeline is back online. Russia is once again heating German homes, fuelling German industry, and using German money to finance its war in Ukraine. But this happy exchange may not continue; the pipeline is still operating at just 40 per cent of its usual capacity, and Vladimir Putin is warning this could fall to 20 per cent next week.

With Germany’s gas reserves just 65 per cent full – thanks in part to state-owned Russian energy company Gazprom’s curious oversight in maintaining...