R arely can an encouraging first estimate of quarterly GDP – up by an unexpected 0.6 per cent, making the UK the fastest-growing G7 nation – have had a greater political impact than when the chancellor seized on it to bludgeon her panicky, confused, rebellious colleagues into sanity. Bolting out of No 11 Downing Street, the recently camera-shy Rachel Reeves declared to semi-startled reporters that the impending Labour leadership election risked “plunging the country into chaos at a time when there is conflict in the world, but also at a time when our plan to grow the economy is starting to bear fruit”. This time, the journalists had no need to bellow their questions at deaf ears from 50 yards. Ms Reeves is right – but recent spikes in the cost of government borrowing have also highlighted, to even the most recalcitrant of Labour MPs, the parlous state of the public finances, and the even more ruinous consequences that would follow a soft-left takeover of the party leadership.…