The UK’s borrowing costs have sailed past five per cent for only the third time since the onset of the Iran war, in a headache for Andy Burnham just days before he enters Downing Street. The yield on the UK’s 10-year government bond – the benchmark for a country’s long-term ability to borrow – climbed by as much as seven basis points on Tuesday morning, after the fragile ceasefire between Iran and the US shattered. The two countries exchanged strikes for a third successive night, in a dramatic escalation of tensions…