What UK involvement in Iran could look like – and the political questions it raises

London: Geraint Hughes does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

At the time of writing, US President Donald Trump is deliberating over whether to join Israel’s air campaign to destroy Iran’s suspected nuclear weapons programme. This is already a contentious issue within Washington DC and the Trump administration. But if the president decides to take the US into a war with Iran, it will have significant implications for the US’s allies, not least the UK.

As the recent strategic defence review emphasises, the US is Britain’s main ally, an essential partner in defence and intelligence.

However, the Trump administration has made clear to its European allies that it no longer regards the defence of the continent as a US national security priority. And the president’s commitment to Nato is uncertain.

It is possible that Britain and other European allies could be publicly pressured by Trump to support any intervention on Israel’s side. The US may expect this in return for the US’s continued involvement in Nato and its readiness to honour article 5 (the collective defence principle, which obliges collective retaliation to aggression against one member) for its allies.

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Given the importance of American military power in deterring wider Russian aggression in Europe – and Trump’s transactional character – this would present Keir Starmer with a particularly stark dilemma.

A purely US air campaign against Iran is feasible. The US Navy will soon have two carrier strike groups in the Middle East region. And the US Air Force’s B2 strategic bombers can launch raids across the globe from bases in the continental US.

The US also has several military bases in the region. However, as was the case with the 1991 and 2003 wars with Iraq, Washington DC will need permission from Gulf Arab allies to use them.

Nonetheless, the Trump administration could request authorisation from the UK’s Labour government to use US airbases in the UK and its overseas territories to support an air campaign against Iran. This would not involve the UK deploying forces, but would require the UK to approve the use of the airbases.

The Diego Garcia airbase in the Indian Ocean would be a useful asset in this case. But its employment would reopen the controversy over its establishment in the 1960s.

It could also call into question the diplomatic deal the UK made with Mauritius last month to cede sovereignty of the Chagos Islands, while keeping this base open. The Mauritians are likely to oppose US airstrikes on Iran.

Britain also has options for direct participation. RAF Typhoon jets stationed at Britain’s airbase in Akrotiri, Cyprus provided air defence support for Israel during the Iranian missile and drone strikes in April and October 2024. They could conduct similar missions now.

But from the Royal Navy’s perspective, it would be difficult to divert the aircraft carrier HMS Prince of Wales from its deployment to the Indo-Pacific, partly because the task group it sails with is a multinational one.

Given that the British armed forces are already overstretched, it is difficult to see whether the UK could provide more than basing rights and air support to the Israelis (if requested).

A discreet commitment of UK special forces (the 22nd Special Air Service regiment and the Special Boat Service) on the ground is conceivable. This can be – and indeed has been – authorised by previous governments without parliamentary debate. But any further British military commitment is likely to cause a political row.

The key question for Starmer and his ministers will not be whether Britain could back a US war against Iran but whether it should. After the debacle of the Iraq war and the ensuing Chilcot inquiry, it is difficult to see how any government – let alone a Labour one – can take Britain into a major interstate conflict on this scale without firm parliamentary support and a solid case in international law.

To this end, the Attorney General Richard Hermer has reportedly questioned the legality of Israel’s preemptive attack on Iran, and has argued that any British military intervention should be limited to the defence of its allies.

We should not forget that Starmer was a human rights lawyer and the head of the Crown Prosecution Service before he became a politician.

Another legacy of Iraq is that it is customary (though not a legal requirement) for prime ministers to seek parliamentary approval for any major military operation. David Cameron lost a vote in the House of Commons to approve airstrikes against Bashar al-Assad’s regime in Syria in August 2013. But he gained parliamentary support for Britain’s commitment to the fight against Islamic State in 2015.

A similar debate now is unlikely to lead to approval of British military intervention in this case. Within the Labour party, there is already widespread condemnation of Israeli tactics and Palestinian civilian casualties in Gaza.

There is little popular appetite for sending British sailors and airmen into a war with Iran. And, given the US vice-president’s own dismissive comments about the military experiences of European allies, the public is also entitled to ask why British servicemen should die or risk breaching international law for an administration that probably will not appreciate their sacrifice.