Strangers to Indian politics can be forgiven if they find the apparent collapse – or at any rate the postponement – of the US-India deal on nuclear co-operation hard to credit.

The agreement was a triumph for Manmohan Singh, the prime minister. It ended a 30-year ban on nuclear commerce and held out the promise of nuclear fuel and technology from the US and others. India has not signed the nuclear non-proliferation treaty and has no intention of doing so. Regardless, the pact, announced this summer after two years of talks, granted the country wide exemptions from existing nuclear safeguards – enough to undermine the global non-proliferation regime. Many governments regretted that India had secured what they believed were indefensibly generous terms. Now India itself is walking away.