Deterrence is the key point of having nuclear weapons

Labour MPs, who had a free vote on the matter, openly contradicted their leader Jeremy Corbyn, in his opposition.

There are in fact plausible arguments that renewing Trident is too expensive and not appropriate for today’s security threats, and these arguments have found favour with respected and expert voices such as the former Defence Secretary Michael Portillo.

But those arguments are outweighed by numerous other arguments. Having a nuclear capability is essential in a nation that has a permanent place on the UN security council.

It is also an essential signal to Nato and our most powerful and important ally, the United States, that the United Kingdom intends – as it has always done – to pull its weight when it comes to helping to defend not just Britain (which is obviously our first priority) but also Europe and the western world.

The debate yesterday, however, illustrated not merely the wrong conclusion of Mr Corbyn and the Scottish National Party, but their naivete. Theresa May scored an open goal when the SNP MP George Kerevan asked if the Prime Minister would authorise “a nuclear strike that can kill a hundred thousand innocent men, women and children?”

She replied: “Yes ... the whole point of a deterrent is that our enemies need to know that we would be prepared to.”

What sort of senior politician could not have seen in advance of Mrs May’s response the obvious answer that the nation’s political leader had to give? That while using a nuclear weapon is plainly a nightmare scenario it is the willingness to use them against aggressive regimes that might just constrain an attack in the first place.

The SNP can take the moral high ground on defence by playing pacifist but Mr Corbyn cannot do so and still expect to make it to Downing Street.