If reminders of the bestial nature of the mullahs' regime were needed, events in Tehran last week did not disappoint.

Last Sunday, the Iranian Parliament ordered the expulsion of British Ambassador Dominick Chilcott and downgraded diplomatic relations with the United Kingdom.

The next day, Iran's Supreme Leader Ayatollah Ali Khamenei incited crowds with his hate-speech, saying that Britain "has a history of humiliating nations, destroying cultural and civilization heritage and taking control of their resources."

And then on Tuesday, Iran escalated its conflict with a rampage directed at the British embassy whereby state-sponsored thugs tore down the Union Jack, shouted "Death to England," smashed windows, defaced walls, and briefly took hostages. Thugs carried placards with pictures of Qassem Suleimani, head of the regime's elite Qods Force, which runs terror networks across Iraq, Afghanistan and Lebanon. Suleimani indirectly has the blood of dozens of British soldiers on his hands.

The attack on the British embassy was in retaliation for tough new economic sanctions designed to further isolate Iran in its relentless pursuit of nuclear weapons. The sanctions provoked especial anger because they were tougher even than those imposed by the United States and other allies. Following the UN nuclear agency report offering new evidence that Iran has indeed mastered the technology required for a nuclear weapons programme, Britain severed all contact with the Iranian Central Bank.

The announcement by Foreign Secretary William Hague that the Iranian embassy in London would be immediately closed and its diplomatic staff expelled is a wise step - but one that must be supported by other equally critical initiatives. There is more that can and should be done to effectively isolate the mullahs' regime, which is the leading purveyor of state sponsored terrorism in the world today.

Prime Minister David Cameron and Foreign Secretary Hague must immediately issue an official statement acknowledging the legitimacy of the Iranian opposition movement, Mujahedeen e-Khalq (PMOI/MEK). This well-organised opposition movement is committed to non-violence and shares common strategic foreign policy goals with Britain: namely, regime change and a democratic, liberal, nuclear-free Iranian future. MEK has provided the world with valuable intelligence about the location of key Iranian nuclear sites.

Not surprisingly, the mullahs' terrorist regime considers the MEK an existential threat and has vowed to eliminate it at all costs, enlisting Iraqi Prime Minister Nouri al-Maliki to deliver the mortal blow to 3400 unarmed MEK members, "protected persons" under the Geneva Conventions, who are refugees living in Camp Ashraf in the Diyala Province, close to the Iranian border.

Twice - in July 2009 and in April 2011 - defenceless Ashraf residents were brutally attacked by Iraqi military forces on Tehran's orders. The most recent assault resulted in 36 dead, including 8 women, and over 300 wounded. Now Tehran's willing partner, Maliki, has imposed an arbitrary and illegal deadline for closing Camp Ashraf - 31 December, when all US military forces will be withdrawn from Iraq - so that he can disperse Ashraf residents throughout the country in an effort to torture and kill them out of sight of the international community.

The UN has officially designated Ashraf residents as asylum-seekers and has asked that the deadline for closing the camp be extended so that its refugee agency, the UNHCR, can complete its work to resettle them safely in other countries.

Active and immediate British engagement at the UN Security Council to protect the 3400 unarmed Iranian dissidents at Camp Ashraf is imperative. No effort should be spared to prevent the Srebrenica-style massacre that will follow after the camp is closed.

Equally, on the nuclear front, Iran ranks as the top pariah state.

When the European Union started negotiations with Iran eight years ago, Tehran had not even completed construction of its only known uranium enrichment facility at Natanz, and it was not enriching uranium.

Today, Tehran is enriching up to 20 percent, installing centrifuge machines in an underground uranium enrichment facility in Qom, building nuclear warheads, and has enough enriched uranium to make four nuclear bombs. European trade with Iran during this time enabled it to fund its nuclear weapons programme.

Engagement has failed to halt Tehran's nuclear drive and sanctions have proved insufficient.

Not since the 1989 furore over the publication of Salman Rushdie's book, "the Satanic Verses," has there been such a violent rupture of British-Iranian relations. Nine years later, Ayatollah Khamenei suspended the death warrant on the British author, on the promise that the British ambassador would return to Iran. But the day after he returned, the Iranian leadership retracted its promise. Britain acquiesced to the deception and did nothing.

The lesson that should have been learnt then is being repeated now. In this era of the Arab Spring the time is propitious to change Iran from within. We must rely on and actively support the people of Iran and their most effective opposition movement, the MEK, to bring about the democratic change which the millions in Iran desire.