On Thursday, diplomats from six world powers will meet in Geneva with a top Iranian official to try and resolve the dispute over Tehran’s nuclear programme. In the seven-year standoff over Iran’s nuclear ambitions, this meeting marks the most critical moment yet. Iran has for years pressed ahead with a nuclear programme that is in large part hidden from the outside world. Iran claims the programme is designed to provide civil nuclear power, but the US and its allies believe it is aimed at acquiring a bomb. If Iran makes further progress, Israel has threatened to attack Tehran’s facilities. Both of these outcomes – Iran with the bomb or Iran bombed – must be avoided. A middle way, a diplomatic solution, must be reached.

The revelation that Iran is secretly building a second enrichment plant near Qom adds urgently to pressure for a solution. US officials say this is an enrichment plant based at an Iranian Revolutionary Guard Base and therefore has military application. They say it is designed to manufacture weapons grade uranium. After the Iraq debacle, the outside world listens sceptically to western intelligence claims. But what is not in doubt is that this plant was kept secret from the United Nations for years. Iran’s claim that it is part of a peaceful civil nuclear programme cannot be taken remotely seriously.