The bodies of Bucha have set a difficult test for the west

Sometimes a war crime is so egregious, and so fully reported, that it cannot but stir the conscience of the west. The My Lai massacre in 1968, Srebrenica in 1995, the British suppression of the Mau Mau rebellion in Kenya, the Rwanda genocide of 1994, the Disappeared of Argentina under the junta in the 1980s or even the dispatches about bodies piled high in Bulgarian town squares by the US war reporter Januarius MacGahan in 1876 were all moments when the defence of ignorance has to be abandoned.

So it is not a foregone conclusion that the pictures of Ukrainian civilians murdered with their hands tied will lead to towns such as Bucha becoming a spur for action when Nato and G7 ministers meet this week in Belgium. Measures such as suspension of Russia from the UN human rights council may have some symbolic value, but the big test is further European economic sanctions that may not just hit Russia but also the EU.

For Zelenskiy, a European embargo on Russian energy, even if it were initially only oil, cannot come soon enough. Latest estimates suggest Russia will earn up to $320bn from oil and gas exports until the end of 2022, which is a third more than a year earlier. The Russian rouble rose on Monday, reversing earlier losses, and the Moex benchmark stock index climbed to levels last seen before Russia sent thousands of troops into Ukraine. These are not the signs of an economy close to collapse.

Scholz, due in the UK later this week, insists Germany will back further sanctions in response to the war crimes, but other ministers insist this cannot include a total energy ban.

A full embargo will end up damaging Germany more than Russia, Scholz argues, and he has rounded on a team of economic modellers for irresponsibly claiming a full embargo would lead only to a 3% fall in German GDP.

In taking up this position Scholz has the backing of Germany industry and finance.

The danger is the debate in Germany is becoming very polarised and entrenched. Ben Moll, an LSE professor and the informal head of the group that produced the modelling, is now suggesting a compromise: an embargo on oil and a tax on gas, with measures to cushion the blow for the poorest.