Why did Putin choose BP?
It is striking, to put it mildly, that - of all the companies in the world that prime minister Putin of Russia could have chosen as a partner on the exploration of an enormous area of the shallow Arctic seas - Mr Putin chose the one associated with the most disastrous offshore oil spill of modern times.
Why would he pick BP as his ally in a venture seen both by hydrocarbon fans and environmental campaigners alike as of huge significance?
Given the horrified reaction of Greenpeace and of a couple of US congressmen to the deal - who allege that America's national security may in some sense be threatened by the linked transaction of BP engaging in a share swap with the semi-nationalised Russian oil giant, Rosneft - perhaps it's a manifestation of Mr Putin's mischievous sense of humour.
That however seems unlikely.
For Bob Dudley, the chief executive of BP - whom I interviewed shortly before midnight on Friday soon after the deal with Rosneft had been signed - it shows that his company has learned the important lessons of the debacle in the Gulf of Mexico (you can hear a good chunk of the interview by clicking here.
BP has set up a new safety division, to make sure that safety is a priority in all its operations. And - perhaps more importantly - it has ceased to delegate to contractors any autonomy over decisions which would have a serious impact on BP's reputation or its finances.
Although the argument may well rage in the courts for years about the balance of blame and financial liability to be distributed between BP and its contractors on the Macondo well in the Gulf of Mexico - notably Transocean and Halliburton - the big lesson for BP was that it was too trusting of Transocean and Halliburton to get it right.
Or to put it another way, Dudley argues that BP has learned the systemic lessons of the Gulf spill.
Here's the interesting thing. Let's say that the US presidential commission into the Macondo accident is correct that the accident highlights systemic risks and possible management weaknesses not only for BP and its contractors and partners, but for all the offshore oil explorers and exploiters.
This, of course, is a conclusion that BP's competitors have denied. They would reject the implication that the Macondo horror could have happened to any one of them.
However prime minister Putin would apparently beg to differ. He seems to believe that a once-bitten BP is now a highly reliable offshore explorer - and has backed that judgement with a contract of huge important to his country's ecology, finances and energy reserves.
All of which may imply that BP has - paradoxically - won some kind of competitive advantage in having been forced so publicly to show that it understands what went wrong in the Gulf and that it is a changed company.
So what should that suggest to the non-executives of Shell, Exxon and the rest? Do their companies need to demonstrate to the wider world why they're to be trusted when finding and extracting oil in challenging environments?