The UK, France and Germany have begun proceedings against Iran over breaches of its nuclear deal.

But what is the row about and will the deal survive?

– What is the deal?

The Joint Comprehensive Plan of Action dates back to 2015, a time when Western governments believed Tehran was dangerously close to making a nuclear weapon.

Along with Iran, signatories to the deal included three European countries – the E3 of the UK, France and Germany – Russia, China and the US.

The agreement eased international sanctions on Iran in exchange for Tehran agreeing to restrictions on its nuclear programme to ensure it was for civilian purposes, and rigorous inspections.

– Did it work?

Iran has not developed a nuclear weapon, the scenario the international community was eager to avoid.

But the agreement ran into trouble after Donald Trump withdrew in 2018, claiming predecessor Barack Obama’s “disastrous deal” allowed Tehran access to too much cash and did nothing to stop its “malign behaviour” in the Middle East.

The reimposition of US sanctions as part of Mr Trump’s “maximum pressure” strategy has eroded the benefits of the deal to Iran’s economy, and in response Tehran has carried out a phased process of stepping back from its commitments.

– What happens now?

While the deal is not yet dead, it has effectively been placed on life support after the E3 started the dispute resolution mechanism.

This was triggered by Iran declaring on January 5 that it was discarding the last component of the limitations imposed by the deal and no longer faced “any operational restrictions” on its nuclear programme.

Under the dispute resolution mechanism, Tehran will be given 15 days to respond, a term which can be rolled over indefinitely – so the move is aimed at buying time to reach a diplomatic solution.

– Will the deal survive?

The UK and its allies felt they had to act to prevent the deal being so badly hollowed out that it no longer fulfilled its purpose of preventing Tehran acquiring weapons-grade nuclear material.

But there is little optimism in Whitehall that merely triggering the dispute process will result in an immediate change in behaviour from Tehran.

Ultimately the process could result in a return to the UN Security Council and the reimposition of sanctions, although that is not what the UK wants.

– What are the alternatives?

Right now, the JCPOA is the only deal on the table and the UK and its allies have publicly confirmed their commitment to it.

But Boris Johnson has also urged Mr Trump to come up with an alternative proposal he would be willing to support, noting that one of the US president’s main objections to the deal is that it was negotiated by the predecessor he loathes.

“Let’s work together to replace the JCPOA and get the Trump deal instead,” Mr Johnson said.