Everyone in Iran, from Supreme Leader Ayatollah Ali Khamenei down, is aware of how the death of a government critic can lead to political instability. The revolution that gave Iran its current political system began in 1978 with street protests, which were brutally put down by the Shah’s security forces. Each death prompted a memorial service, which rallied protesters, who in turn attracted the bullets and batons of police. That cycle of repression and protest fomented the revolution in 1979.

So the death on 19 December of Grand Ayatollah Hossein Ali Montezari, an outspoken critic of the government, will have been met with concern by the powers in Tehran.

His funeral reportedly attracted hundreds of thousands of protesters, demonstrating the depth of resistance the regime now faces.

President Mahmoud Ahmadinejad appears unsure how to proceed. He has few options, and none of them are palatable. The arrest of any leader of the ‘Green’ opposition movement is unlikely to quell the protests, while brute force could provoke more violent opposition. Compromise appears unlikely, although the chances of a ‘grand bargain’ among the divided elite cannot be ruled out.

Without a return to political normality, the regime’s authority is compromised. It is too soon to predict its demise, but the situation represents a serious threat. In many ways, the government is no longer in control of events, a precarious position for any regime to be in.