Garvan Walshe is a former National and International Security Policy Adviser to the Conservative Party.

The Supreme Leader was in reassuring mode: “America and Israel remain our enemies.”

It is as though he could be expected to continue:

“We have just negotiated an agreement with the Great Satan, so, I would like to ask you, as loyal guardians of the revolution, to show a little circumspection. On Friday, no longer chant “Death to America.” Replace it with something a little bit more moderate: “a jolly good kicking to America!” should suffice.”

The agreement between the five permanent members of the security council, Germany, and Iran will neither destroy Iran’s nuclear programme nor prevent her developing a bomb, but it might postpone it by just enough. Benjamin Netanyahu can explain why.

Some 12 years ago when he was out of power, his political career apparently eclipsed by Ariel Sharon’s, speaking in rooms so small and meetings so insignificant that even the greenest of Conservative staffers (like me) were invited, he made a habit of declaiming that we, the civilised world, had, at most “a thousand days” to prevent Iran’s acquisition of this genocidal weapon.

Central to his thesis was the idea of two clocks: a political clock (time running out for the Iranian regime) and a nuclear clock (the time needed to perfect a bomb – to be launched on a missile, or even trundled across the border by truck to kill the people of Israel).

It seemed very briefly, during the summer of 2009, that the political clock had struck first. Millions of Iranians took to the streets protesting peacefully against a rigged election. So huge were the protests that they were suppressed only with the help of thugs brought in from Jeremy Corbyn’s “friends” in Hizbullah.

The nuclear clock, despite the best efforts of Western intelligence agencies’ cyber sabotage and assassination programmes, continues to tick. Without the deal, it is estimated that Iran came as close to “breakout capability” (the time needed to produce a bomb after exiting the Non-Proliferation Treaty) as two months – far to little time for the world to do much about it without going to war. The agreement sets the nuclear clock back around ten years, perhaps twice as much as a war would have done.

Crucially, it puts time back on Mr Netanyahu’s political clock.

The Iranian regime is exceedingly unpopular. Iranians have had enough of the repression, the personality cult, the official restrictions on freedom, the unofficial intimidation by pro-regime militia, and the militarism it has promoted. They have by some distance the most favourable opinion of Jews in the region – perhaps on the basis that if the Ayatollahs don’t like them, they must be doing something right. Unlike the Greeks, shocked that an East German-born Chancellor wouldn’t lend them the money to try communism, the Persians have learned that Islamic fundamentalism doesn’t work.

This matters now, because the Supreme Leader himself will not be with us for much longer. The choice of his replacement falls to a body known (House of Lords reformers, take note) as the “Assembly of Experts”. It is up for re-election next year, and reformists, boosted by the lifting of sanctions that moderation will have secured, are expected to win.

The “principlists,” as the pro-regime forces as known, will not give up without a fight. The Revolutionary Guard and other hardliners remain powerful. They only acquiesced in this deal, a coup for their internal enemies, because Iran is overstretched in Syria and Iraq needs the money.

The deal remains a gamble. The hardliners will, it is prudent to assume, try to cheat, and the sanctions do not “snap back” as automatically as Barack Obama would have us believe. But when the agreement expires in 2025, there is a good chance that Iran will have become a very different place.

What, then, of Netanyahu? If he is convinced that the only way to save Israel from destruction is to bomb Iran’s nuclear sites, then he has an overriding obligation to launch an attack. But it is surely significant that his most senior military and intelligence chiefs, and their predecessors, do not think that one is justified. Though the agreement gives Iran ten years to refine its nuclear technology, it also gives the countries the Supreme Leader has insisted are still his enemies ten years to make sure they put contingency plans in place should it fail.