There is nothing like an oil spill to stir emotions. The leaking Macondo oil well in the Gulf of Mexico is a serious incident and the parties involved, led by BP, must prepare for a worst-case scenario. BP began drilling a relief well at the weekend, but that could take three months, with leakage continuing all the while. It is an environmental calamity in the making.

It remains too early to judge this incident and its scope to damage BP's finances and reputation. The company underestimated the initial scale and cost of the accident when it reported first-quarter results last week, and has given the impression that it has since been playing catch-up, despite chief executive Tony Hayward's commitment to the clean-up and his presence on the ground. BP says the clean-up effort is costing more than $6m a day. But the costs of such a complex and dangerous task keep rising.

BP denies, credibly, that it is at fault for the accident. But it is BP's oil that is spewing into the gulf, which is what matters now; legal responsibility remains to be apportioned. The Obama administration has raised the stakes for everybody involved in this incident with its threat to keep its “boot on the throat” of BP to pay for the clean-up. Yet just because BP has the deepest pockets does not make it a piggybank to be raided.