What are Britain's interests in the Israel-Iran conflict?
The United Kingdom has four main interests in Iran.
First, that Iran does not develop nuclear weapons and thereby further damage the cause of nuclear non-proliferation.
Second, that a crisis which produces waves of refugees does not envelop Iran.
Third, that international norms regarding political assassinations and acceptable targeting in warfighting are maintained.
Fourth, that Middle Eastern energy infrastructure and logistics remain operational so that energy prices do not spike.
The current actions of Israel (and now the United States) cut against every one of these interests.
On the first of these interests, it is difficult to imagine anything more likely to push Iran to accelerate its efforts to proliferate (or convince other nations that they might need a bomb) than the events of the last week. Non-proliferation efforts have therefore been significantly set back. Even if the facilities and reactors, apparently buried beneath many feet of solid granite, are completely destroyed, it would only delay the programme, which would surely be a priority in future for any Iranian government.
Israel, though, appears to want to remove the present Iranian political leaders in order to foment the breakup or federalisation of the country, and perhaps precipitate a full-blown civil war (The Jerusalem Post has published an opinion editorial demanding the US help with exactly these aims). This would be a humanitarian catastrophe. It would also almost certainly draw Turkey, Azerbaijan, Pakistan, the Gulf Monarchies, and perhaps China and the US, into the theatre. Most importantly, though, it would produce a wave of Europe-bound immigrants larger than those that hit after Western powers fomented the Libyan and Syrian Civil wars. Israel would be happy, as Iran would (at least for some years) be too weak to be a threat anymore, but an Iranian breakup, civil war or chaotic regime change would obviously be against UK interests.
On the third matter, our support for Israel's assassination and decapitation strikes is short-sighted. If, say, Russia or Argentina commenced a war by killing Britain's political leadership, senior members of the Civil Service, senior staff officers, and the heads of Britain's intelligence services and police, then attacked our nuclear facilities and murdered British nuclear scientists to make repair and regeneration efforts more difficult, I think we would feel that that was beyond the pale, even by the standards of war. And that's putting it mildly. There used to be unwritten yet strict prohibitions against such acts, but we appear to have endorsed setting them aside.
Finally, while Iran has not yet responded to Israel's attack by attempting to close the Strait of Hormuz (a trifling task) or attacking energy infrastructure in other Gulf countries, such steps are very much on the table now the US has joined Israel's air attacks on Iran. Even the awesome might of US air power will not be guaranteed to suppress such efforts. If the Strait is closed, and if energy infrastructure is attacked, oil prices will surely spike, perhaps to over $100. Such prices would not only lead to higher inflation, but could trigger recession.
For the above reasons, it is in Britain's interest to seek an urgent resumption of negotiations between the United States and Iran, and to call for an end to hostilities. Or, we could instead cheer on the Israelis, because we love the idea of sticking it to the Muslims, or because we have imported yet another American political pathology, or just because we can't glance a foreign war without taking sides and getting into tribal arguments on Twitter.
