What he himself accounted one of his biggest foreign policy achievements was in fact president Barack Obama's greatest failure. The Iranian nuclear deal lifting crippling sanctions in return for time-limited assurances that Tehran would stop developing technology that would give it nuclear weapons was ill-conceived from the outset. There are legitimate questions to be asked about any sanctions. Governments can generally circumvent them. They are commercially unpopular. There are always bankers, oil traders, arms dealers and shady middlemen willing to reap greater profits from dealing illicitly with sanctioned regimes. Moreover, there are generally other states that will turn a blind eye, if not actively assist a sanctioned country in escaping, to some degree at least, its economic isolation. But Iran was an exception. For sure the ayatollahs' regime was getting outside help, not least from across the border in Russia, but the extent of the sanctions and the ferocious manner in which Washington pursued their implementation actually meant that Iran was in a deepening economic mess. The shortages of goods, the breakdown in infrastructure, in the oil industry and the general decay of life in Iran were fueling political unrest that threatened the regime's existence. Obama and his secretary of state John Kerry rejoiced when the impact of a collapsing economy brought the Iranians to the negotiating table in Geneva. The big stick had worked. But thereafter, everything went wrong. In years to come academics will study the Iranian negotiations over the end of sanctions, as a masterclass in diplomacy. The Iranian chief negotiator, the urbane Mohammad Javad Zarif ran rings around the Americans, seeming to accept a deal only to resile at the last minute and go back to minute detail that frustrated and exhausted his opponents. It was a bravura performance. In the end against the urgent advice of his allies in the Arab world, not least here in the Kingdom, Obama was prepared to go for any deal that would secure something that he could present as a shining foreign policy victory. But almost before the ink was dry, the Iranians demonstrated their bad faith by obstructing the full inspection of their nuclear facilities by the International Atomic Energy Agency. Now this week they have carried out the test of a medium-range ballistic missile in flagrant contravention of the deal they signed. The Trump White House and Republicans on Capitol Hill are rightly looking to act decisively in response to this blatant violation. But, thanks to Obama's deeply ill-judged lifting of sanctions, the options open to Washington have been severely limited. The minute it was given access to its frozen billions in banks around the world, the Iranian regime quickly moved them to banks less likely to respond to renewed financial sanctions. In addition, Iran has been busy with a strategic campaign letting lucrative contracts to US and EU companies who are now permitted to trade with Tehran. Thus a return of sanctions will have an impact on US and EU business. To reimpose penalties on Iran at this juncture is going to have a minimal effect. The Iranians are not stupid. They have seized the opportunity given them by Obama's huge error to prepare for a return of their economic isolation while they press on with their nuclear weapons program. Obama's chickens have come home to roost.