Garvan Walshe was National and International Security Policy Adviser to the Conservative Party until 2008.

There’s a new diplomatic game afoot. Today, negotiations over Iran’s nuclear programme begin in Geneva. After years of intransigence and rejectionism, Tehran has been sending out very strong signals that might be ready to make a deal.

As always in these situations, what the late, great Conor Cruise O’Brien called “the peace processors” are out in force. They insist that Iran’s emollient new President, Hassan Rouhani, needs to bring concessions back from Geneva, otherwise his Supreme Leader will cut off his support.  There’s a good deal of truth in this. Iran, far from being a cartoon theocracy run by mad mullahs, has a complex, if undemocratic, political system. Rouhani has opponents for whom negotiations are a tactical error and enemies for whom they wrong in principle. Iran’s Keyhan newspaper (often described as ‘conservative,’ it is far more fiery than, say, the Daily Telegraph) has strongly condemned this latest initiative.

Yet this argument is often pushed too far. In the early days of the Northern Ireland peace process (before the IRA decided it hadn’t obtained enough concessions, and bombed Canary Wharf and Manchester to remind people that they hadn’t gone away), the peace processors made much of of something called TUAS. TUAS, the public were assured, stood for the rather vegetarian Totally Un-Armed Strategy, but as it transpired it was nothing of the sort. Instead, as O’Brien explained, it signified the, from their point of view far more sensible, Tactical Use of the Armed Struggle.

No doubt these negotiations offer a huge prize: a successful deal would remove Iran’s military nuclear capability from the Middle East, without risking a war; it would cut the risk that Egypt, Saudi Arabia and perhaps Turkey would respond to an Iranian bomb with one of their own, and it would improve Israel’s strategic situation immeasurably. While Iran would still have plenty of means to stir up trouble though Hezbollah or in Bahrain, it is obviously far better that it pursue those activities unprotected by a nuclear umbrella.

But the negotiations will not succeed if the United States and the EU make too many concessions up front.  Like the IRA, whose armed struggle was not going well, but didn’t find itself on the brink of defeat either, Iran hasn’t been ‘driven to the negotiating table.’ She has options. Tehran has chosen to give negotiations a chance because sanctions have begun to posed massive economic difficulty. Financial transactions have become increasingly expensive and insurance for its oil tankers prohibitive. Because of this rationale, it’s not only a matter of giving Rouhani enough to show that talks ‘are working.’ Lift too many sanctions at once, and they will have, from Iran’s point of view, worked all too well. Under less economic pressure, the mullahs’ reason to negotiate disappears.

We will read a lot in the coming months or perhaps years about the cities of Arak, Natanz and Fordow, levels of uranium enrichment, and the regime under which nuclear sites are to be inspected. The details about how they are dealt with will be important, but the essential ingredient is time. The cost of Iran’s pursuing a nuclear bomb increases the longer it takes to achieve as economic hardship mounts up. When the time comes to exchange concessions, the aim should be to slow the programme down, where possible giving up only symbols in exchange.

It is essential too to lower Iranian expectations of Western reasonableness. Sinn Fein-IRA had managed to secure the 1998 Belfast Agreement without giving up its weapons. Only Democratic Unionist intransigence eventually saw ‘decommissioning’ happen. Much foreign policy analysis assumes the West’s role is to play almost the role of an impartial observer, but we have hardliners on our side, too, and if negotiations are to get Iran out of her economic mess, those Western intransigents will also need to be given something.  However reasonable that nice Mr Obama may sound, he will need to obtain the assent of a group of fanatics so resolute that they are willing to bring economic chaos on their country in a dispute over healthcare administration. If Iran’s intentions are serious, she will need to give thought to winning at least some of them over.