Tensions between Pakistan and the US often made life tricky for Matthew Barrett, a young man from Alabama living in Islamabad, but when he was arrested in May, things went from bad to worse, as he has revealed in a letter smuggled from his jail cell Plagued by old resentments, accusations of infidelity and violent squabbles that end in the diplomatic equivalent of plate-smashing, Pakistan and the US have long been compared to a crisis-stricken married couple. It is a forced marriage, officials like to say, or an unhappy Catholic one: