Would it not be a good thing if Boris Johnson had been speaking for the Government in Rome, last week, when he said, “You’ve got the Saudis, Iran, everybody, moving in and puppeteering and playing proxy wars”?

A spokeswoman for Theresa May said yesterday that the Foreign Secretary’s comments “did not reflect Government policy” but, given that what he said was eminently sensible, wouldn’t it have been better if they did? Malcolm Rifkind, a former foreign secretary, questioned today whether Johnson had the “temperament” for the job.

But if by “temperament” we mean the ability to avoid telling the truth about the Saudi Arabian regime, should we not welcome a Foreign Secretary who tells it like it is? After all, what is the worst that could happen?

The alliance would be over

If Johnson had been speaking for the UK Government when he said the Saudis were fighting proxy wars, “twisting and abusing religion and different strains of the same religion in order to further their own political objectives”, the Saudi royal family would have been offended. Presumably they were offended anyway – but as long as Johnson is repudiated by his Prime Minister, everyone can pretend, diplomatically, that the UK-Saudi alliance continues to be strong.

The Saudis know, after all, what most Western politicians say about them privately, and that diplomacy is built on hypocrisy. But if the UK Government’s policy changed, co-operation would be at an end.

Boris Johnson: Saudi Arabia is playing proxy wars

The sale of arms would cease

The most obvious and visible effect of breaking off relations would be the end of British arms sales to the Saudi government. This would cost thousands of jobs, which is never a good argument on its own, but is something that no one can treat lightly.

Johnson was uncomfortable on the The Andrew Marr Show on Sunday as he defended arms sales to Saudi Arabia, saying, in effect, that he was very worried about it but that there was no hard evidence of British weapons being used in human rights violations in Yemen, where the Saudis are fighting on the side of the government against a Shia insurgency.

Intelligence co-operation would end

This is always the trump card played by prime ministers in defence of the geostrategic relationship. Tony Blair and David Cameron in particular used to suggest that Saudi intelligence co-operation was directly responsible for averting horrible terrorist attacks.

The trouble is that the benefits of co-operation have to be secret; normal citizens have to take the word of senior politicians and spy chiefs that the intelligence is as valuable as they say it is. That has become harder to do after the intelligence failure of the Iraq war, but again it is not something that can be dismissed lightly.

Reform in Saudi might be set back

A more principled argument is the age-old “engagement is better than isolation”. This is that the best way to promote human rights, democracy and equality for women in Saudi Arabia is to engage with the regime, and especially with the more reform-minded elements of it.

That was the argument behind the prison services contract which Theresa May supported as Home Secretary – although it had actually been the responsibility of Chris Grayling as Justice Secretary, before he was replaced by Michael Gove, who cancelled it.

A policy of telling the Saudi regime what a backward-looking, regional trouble-making despotism it is might strengthen the conservative elements of the large and faction-ridden ruling family and put back the cause of progress.

Iran might be emboldened

Finally, breaking off relations with Sunni Saudi would tip the balance of regional power in favour of the Saudis’ Shia rival, Iran. Johnson may have written a column for The Daily Telegraph 10 years ago saying, “Give Iran the bomb: it might make the regime more pliable,” but it must be doubted whether he believes it now.

Boris Johnson 'not worried' about Trump and Putin's relationship

(Once again, that is the trouble with appointing a newspaper controversialist to high office: he will always be followed by his own disobliging quotations.)

Barack Obama’s achievement of a deal with Iran, by which it has accepted constraints on its ambition to acquire nuclear weapons, may not be undone by Britain going it alone in censuring Saudi Arabia, but it might help Donald Trump to undermine the current President’s policy.

We would finally have an ethical foreign policy