Clarke sacked and Prescott downgraded - these were easy to predict, as both had been mired in scandal, and both had plainly been promoted above their ability. But Jack Straw is one of the few senior ministers who appeared to be coping with his workload. Why did he have to be moved, so urgently that it required the breakup - at least for a few hours - of the FCO?
It seems to be his public insistance that war with Iran is both 'inconceivable' and 'nuts'. I don't know Downing Street's current thinking on the matter, or the state of the intelligence on which both Blair and Bush rely. But official policy in both the US and UK is that all options are on the table. Straw's sin was the same as Joseph Patrick Kennedy's (not to be confused with a famous drunk driver, who has the same names in a different order) in 1938. Kennedy -then US ambassador to London - assured Nazi Germany that the US would not intervene in a European war on Britain's side. He was right. The US did not enter the war until after it was itself attacked. But FDR did not want Hitler to know the US was planning to stay neutral. He wanted him to fear the possibility of US intervention.
Even if you have decided not to go to war, it is not always sensible to say so. And it is crazy to give such a pledge on behalf of your boss, when he is being deliberately vague.