An epic oil surplus in the spring of 2020 prompted an unprecedented reaction from Opec-plus to avert a total collapse of oil markets and prices have firmed. But the future is anything but certain.

How durable is the Opec-plus alliance? How will the group maintain discipline as prices stabilize? US shale and producers outside the alliance have had to shut in production because of low prices, but at what point will that production start coming back, and how quickly?