When this week's trip to Washington was first pencilled into David Cameron's diary, the Prime Minister must have been looking forward to a chance to make acquaintances in the White House and to address some of the pressing challenges facing our two nations. Instead, he walked into a toxic row about a convicted terrorist, a vilified oil company and a decision taken by the Scottish Executive before he was even elected to office.
A group of US Senators are up in arms about what they see as BP's role in the release last August of the man convicted of the 1988 Lockerbie bombing, Abdelbaset Ali al-Megrahi, on compassionate grounds. They claim that one of the reasons for the release of the terminally ill Megrahi was to help the giant oil company secure a lucrative deal with Libya.
There is nothing wrong in scrutinising BP's lobbying activities. But this appears to be the wrong target. There is no evidence that BP influenced the decision of the Scottish Executive. And the fact that Megrahi is still alive despite being expected to survive only months after his release (presented as evidence of some sort of conspiracy) is neither here nor there. There is always uncertainty over the life expectancy of patients with terminal illnesses and there is no reason to believe that the doctors who examined Megrahi made their diagnoses under political pressure.
There is also an elephant in the room that politicians on both sides of the Atlantic cannot refer to: the likelihood that there was a miscarriage of justice in the 2001 trial that found Megrahi guilty. Jim Swire, the respected campaigner for the Scottish victims of Lockerbie, is among those convinced that Megrahi was not responsible for the atrocity. The fact is that Megrahi had been given leave to appeal against his conviction and might well have been set free anyway. That would, of course, have been far more embarrassing to Washington and London than his release on compassionate grounds.
There is cynical posturing and dissembling on all sides. Mr Cameron said in Washington that it was wrong to let Megrahi go. But he would probably have greeted the decision of the Scottish Executive to send the Libyan back to Tripoli with the same relief as the previous Government did. The US Secretary of State, Hillary Clinton, says "that Megrahi is living out his remaining days outside of Scottish custody is an affront to the victims' families". But she must know that large question marks hang over Megrahi's original conviction. And would these American senators be pushing this issue so hard were there not political capital to be made out of attacking BP in the wake of Gulf of Mexico oil leak?
The whole business is a mess. A superstructure of outrage has been built upon what looks very likely to have been an act of realpolitik: Libya gave up Megrahi in order to improve relations with the West.
It is legitimate to continue to examine the Lockerbie atrocity and any questionable deals done in its aftermath. But it does no service to the victims of the bombing to press for the recall to prison of a man whose guilt is so much in doubt. Nor does it do any service to the victims of BP's incompetence in the Gulf of Mexico to attack the company for its business dealings with Libya.
There are daunting challenges facing both America and Britain – from managing the withdrawal from Afghanistan to negotiating the ongoing economic crisis – and we have a common interest in our leaders solving them together in the spirit of co-operation. The sooner this confected transatlantic row is allowed to expire, enabling them to turn their attention to more current problems, the better.