Attack Ed Miliband and sing up the long-term economic plan: that is the now obviously useless scheme devised by the Tory party’s strategy adviser Lynton Crosby, against the best advice of Plutarch and Aristotle.

The Greek biographer Plutarch (c. ad 100) could have advised him against the attack-dog tactic. In an essay entitled ‘Turning enemies to one’s advantage’, he pointed out that the presence of enemies kept one sharp; to distress the enemy who hated you, ‘be a man, show self-control, tell the truth, treat those who come into contact with you with generosity and fairness’.