Iran’s ransacking of the British embassy in Tehran, which prompted the recall of all British embassy staff and the expulsion of Iranian diplomats from London, means that the chances of miscalculation by both sides in this spiraling crisis have suddenly intensified.

Iran has deliberately set itself on a path of isolation, even though Britain, long considered the “little Satan” in Iran alongside the American “Great Satan,” says that it is not severing diplomatic ties. But cutting channels of communication with Tehran, where radicals were already in the ascendant, contains other dangers at a time when Iran’s nuclear program is back in the diplomatic foreground.

Adm. Mike Mullen, in remarks before he left his post as chairman of the Joint Chiefs of Staff, warned that the lack of direct communication between the U.S. and Iran since 1979 mean that “many seeds for miscalculation” had been planted. “When you miscalculate, you can escalate and misunderstand.” He was obviously talking about the potential for armed conflict.

Those lines have now been cut between London and Tehran, too. One immediate effect will be that we can say goodbye to a new round of talks between the so-called “5 + 1” process, involving the permanent Security Council members — U.S., U.K., France, Russia and China — plus Germany on curbing Iran’s nuclear ambitions.

But it’s also likely that the covert war under way between Western powers and Iran will escalate.

Britain should have been expecting a tough reaction from Iran after targeting the Iranian central bank for sanctions, which Tehran had said it would consider an act of war. Despite calls from Congress to do the same, the Obama administration — wisely — held back from such a measure.

The latest sanctions were introduced in the wake of a report by the U.N. watchdog, the International Atomic Energy Agency, which blew apart the international coalition that had earlier targeted Iran with U.N. sanctions. Russia in particular accused the IAEA director-general of publishing a “biased” report that pointed to evidence of weaponization activities by Iran prior to 2004 but failed to produce a smoking gun.

The IAEA report was a deliberate escalation in the crisis with Iran, and enabled Israel to renew its threats of military strikes. Now the Iranians have hit back. With elections looming in both Iran and the U.S., it will take cool heads to walk us back from this escalating crisis.