Diplomats and Iran analysts said that the storming of the British embassy in Tehran revealed the role of a growing, radical actor in Iranian foreign policy: the Quds Force.

There is certainly plenty of debate about how far up the chain of command the orders for Tuesday's embassy invasion went.

The force is the external operations wing of Iran's Revolutionary Guard corps (IRGC), one of the regime's most powerful institutions, with extensive economic and financial interests across the country.

Some of the rioters at the embassy on Tuesday held aloft pictures of the Quds Force commander, Qassem Suleimani, around whom a personality cult is developing. There are claims that a known Quds commander was in the crowd.

In his statement to parliament, William Hague said that the damage done to the embassy and the residential compound was done by 200 "student Basij militia", but diplomats note that according to a recent restructuring by the Supreme Leader, Ali Khamenei, the Basij serve as a youth arm of the Revolutionary Guard.

Meir Javedanfar, an Israeli-Iranian analyst, said: "The Basij falls under the command of the IRGC who answer to Khamenei. Basij members don't turn up in front of embassies, unless they have permission from the IRGC as well as operational procedures, which would certainly include whether to launch a physical attack or not."

Conspicuous in their dark, ascetic clothing, the Basij crushed the opposition street protests of 2009 by driving into crowds of demonstrators on motorcycles wielding batons and knives.

Some diplomats believe that as the target on Tuesday was foreign, the Quds Force was "in the driving seat".

Another western official believes that the Quds Force's leading role is restricted to operations overseas, "but the mob see Suleimani as an icon as he is taking on the enemy directly".

Suleimani has made clear he has big ambitions. In 2008, he had a phone text sent to General David Petraeus when the CIA director-to-be was running the war in Iraq, informing him that he, Suleimani, was the man he should be dealing with on Iranian foreign policy.

The text read: "General Petraeus, you should know that I, Qassem Suleimani, control the policy for Iran with respect to Iraq, Lebanon, Gaza, and Afghanistan.

"And indeed, the ambassador in Baghdad is a Quds Force member. The individual who's going to replace him is a Quds Force member."

Western diplomats in Kabul say that the Iranian ambassador there is also a Quds Force officer. The force has a particularly heavy presence in Afghanistan's western Herat province, where its primary focus appears to be to prevent Shindand air base, near the Iranian border, staying in US hands after the 2014 transition.

Turkish officials meanwhile have confirmed western allegations that the Quds Force is active in Syria, and is a powerful player in Iraq.

In October, the US accused Suleimani and the Quds Force of being behind a plot to blow up the Saudi ambassador in Washington when he was dining in his favourite restaurant.

If true, and many observers cannot believe that a commander as senior as Suleimani could be so reckless, it would be a sign that the Quds Force is seeking to expand its operations to confront Iran's two greatest enemies, the US and Britain, directly.