David Cameron appears to have come to the view that Jeremy Corbyn will be the next Leader of the Opposition. Hence the Prime Minister’s decision to break his silence about the Labour leadership contest and question whether Corbyn can be trusted with the nation’s security:

My concern is that we do everything we can to protect and enhance the security of the United Kingdom. And the idea that we’ll be stronger and more secure by leaving NATO, as Jeremy Corbyn suggests, or by comparing American soldiers to ISIL, I think this is absolutely the wrong approach and would make Britain less secure and that will never happen under my watch.

This question of trust is one reason why Corbyn would be such a disastrous Labour leader. Anyone who agreed to serve as part of his shadow ministerial team would at once be asked: Do you agree with Corbyn about Hamas? About Russia? About Poland? About the United States? About ISIL? About the IRA?

A maverick backbencher can challenge every assumption which underlies our post-war security, and even garner a degree of respect for upholding contrary views with obstinate constancy over a period of several decades. It is harder to see how a Leader of the Opposition can do so.

For the Leader of the Opposition is by tradition allowed to see the intelligence gathered by our security services on current questions of defence and security policy. Could Corbyn and his friends be trusted not to pass secrets to the Russians and to others who have behaved in what most of us would regard as an outrageous fashion? On the contrary, they would consider it their duty to pass on everything they could get their hands on. As Lord Tebbit says of Corbyn in today’s Mail on Sunday:

The sympathy he has shown for terrorists from the IRA to Islamic State shows he is not a man who can be trusted with matters relating to state security and the safety of the realm. I would not trust him even to take a letter to the Post Office.

Many Labour people agree with Cameron’s view that Corbyn is heading for victory. Hence Betty Boothroyd’s cri de coeur in today’s Sunday Times (£), ending with the words: “My old party is galloping towards the precipice. I urge it to heed the jagged rocks before it is too late.”

For Corbyn’s closest supporters, crashing the party onto the jagged rocks is part of the point. Whether at home or abroad, they are not interested in security. They want to create a crisis which will be resolved (or so they fondly imagine) by a revolution.

Cameron is right to warn that Corbyn cannot be trusted on security, and Boothroyd is right to see Labour in imminent danger of destruction.