President Barack Obama meets Britain's prime minister, David Cameron, for talks in Washington on July 20th. The BP oil spill in the Gulf of Mexico and allegations over the company's involvement in an “oil-for-terrorists” deal with Libya are likely to be on the agenda. BP is under pressure to satisfy government officials that the containment cap placed on the leaking well on July 15th is holding. Using the government task force's upper estimate, as many as 4.4m barrels of oil have escaped into the Gulf. This would make it the largest accidental oil spill in history (military attacks have created far bigger spills). Despite that, this quantity of refined oil is enough to keep America's cars and trucks on the road for just a quarter of a day. BP has spent almost $4 billion on clean-up costs to date, with the eventual total estimated at $39 billion.