Italy has produced five prime ministers in six years. The latest came in on Saturday, when the 39-year-old mayor of Florence and new leader of the centre left Partito Democratico (PD), Matteo Renzi, was sworn in. Like each of his predecessors, he promised to save Italy from itself. The political, legislative and economic systems would be overhauled. The incessant rot that was threatening to turn the euro zone’s third largest economy into a sunny Mediterranean backwater, dotted with the palaces of Renaissance popes and modern-day Mafiosi, would be halted.