As “frozen conflicts” go, the simmering arch-rivalry between India and Pakistan, dating from the partition of the subcontinent, has an alarming ability to boil over, even if the conflict has recently been contained mostly to remote Himalayan valleys or the Siachen glacier.

This weekend’s overture to India by Asif Ali Zardari, Pakistan’s president, in which he renounced any first use of nuclear weapons – part of the underpinning of Pakistani deterrence doctrine – and called for an economic union with India, was therefore startling and welcome.