The Prime Minister comes back from his well-earned holiday to the biggest political crisis of his premiership. The immigration and refugee issue engulfing Europe has the potential to wash his government away. David Cameron needs to summon up all the authority a British Prime Minister has at his disposal, not simply to confront but to surmount this mega-crisis.

If he doesn’t realise now, he soon will that there’s not one migration crisis he faces, but four which are inter-related.

Last week the Government published figures on net migration into this country. They were little short of catastrophic for a government that rightly believes in setting a limit on the numbers of newcomers to our shores. The Government’s current strategy has failed dismally. But the Prime Minister must realise that what we have so far seen on this score is merely the rumbling of a political Mount Vesuvius.

Any pretence he had that he could control net migration by gliding around Europe prattling on about restricting Britain’s social security benefits and tax credits must be relegated to the political kindergarten.

If David Cameron doesn’t realise now, he soon will that there’s not one migration crisis he faces, but four which are inter-related.

The first of the linked crises is the mass internal migration of people within Europe. When push comes to shove, the Prime Minister won’t carry the country with him in the long promised referendum on our membership of the European Union if UK voters believe that he hasn’t tackled seriously the European question.

At some stage the country will summon up the political will to lay down the minimum red and blue lines on which the Prime Minister has to renegotiate with Europe. And the first must be that we regain physical control of our borders – even if it is only temporarily.

The Prime Minister doesn’t stand a cat in hell’s chance of moving towards his quite properly defined goal of 100,000 net migration a year without being able to control our borders within Europe.

He has got to make it plain to Mrs Merkel that he won’t be able to win a referendum unless Britain can temporarily control the number of Europeans migrating to Britain to work. She must know it’s a make or break issue. No control, no British membership. She’d be left with the fiscal basket case of an EU.

Last year a major grouping accounting for the enormous increase in newcomers came from Europe. That cannot continue.

Any pretence the Prime Minister had that he could control net migration by gliding around Europe prattling on about restricting Britain’s social security benefits and tax credits must be relegated to the political kindergarten

The Government’s current strategy has failed dismally. But the Prime Minister must realise that what we have so far seen on this score is merely the rumbling of a political Mount Vesuvius

Last year a major grouping accounting for the enormous increase in newcomers came from Europe. That cannot continue

There are three more immigration crises which are now beginning to erupt at one and the same time. First, not since the end of the Second World War have we seen so many people beginning to move around the world in fear of their lives. The idea that Greece and Italy on their own can hold these unbelievable numbers of people on the move, granting refugee status and returning economic migrants to their home countries, unaided, is childlike.

Here is a lesson that Mr Cameron can begin to teach his fellow EU heads on the kind of Union Britain wants to lead. My guess is the country is fed up with having rammed down its throat unnecessary policies whose only purpose is to fulfil the centralised European vision that was envisaged by the founding fathers of the European project.

Britain, and our fellow members of the EU, need an open-looking Europe that has the ability and energy to respond to the crises that confront our Community and the world. Mr Cameron needs to call for the formation of an ad hoc European border force whose existence will be limited to the duration of the present crisis.

This temporary border force must be given the resources, manpower and intelligence so that it can begin to distinguish between refugees fleeing in terror for their lives and economic migrants who are seizing the opportunity to come here to work.

Our response to the refugees must encompass the following strategy. Can we shame Europe into following our lead by using our huge aid budget to ensure that people can settle safely with dignity and hope, as near as possible from the terror from which they have fled? This entails a revolutionary rethink on what life should be like in refugee camps.

Britain, and our fellow members of the EU, need an open-looking Europe that has the ability and energy to respond to the crises that confront our Community and the world

This temporary border force must be given the resources, manpower and intelligence so that it can begin to distinguish between refugees fleeing in terror for their lives and economic migrants who are seizing the opportunity to come here to work

There then needs to be a combined European response to the housing of genuine refugees. Britain must insist that the international obligations to refugees are fulfilled and that refugees must register their status as soon as they land on safe European ground. The Prime Minister will not be able to carry that vital policy in the country unless he’s shown to be up to the challenge of curbing economic migration.

And it is mega economic migration which is the third crisis to be faced. The ad hoc EU border force must have the resources and the courage physically to send back economic migrants to their country of origin. We mustn’t get queasy over this policy.

Implementing this strategy will be very unpleasant as many of the economic migrants put up a fight to stay. But the British public will have a stomach for whatever it takes to distinguish the economic migrants providing it knows that refugees will find a safe haven.

The fourth issue facing us is the threat of terrorist inflitration posed by the mass movement of people. Tackling it will entail combining the intelligence forces of Europe with the work of the ad hoc border force.

Anybody who thinks ISIS is just a collection of thugs who have been lucky in overrunning a large part of the Middle East ought to be given a tablet and told to lie down in a dark room.

If ISIS has shown anything it is that it knows how to fight Western democracies on their soft underbelly and we imperil our future if we underestimate its intelligence for a single moment.

The existence of the Government is small beer compared to this country’s very stability, which is now under threat. It will need a degree of political determination by the Prime Minister which, so far, there has been no need for him to show

ISIS’s high command will have already begun to use the chaos engulfing Europe’s borders to get sleeping ISIS agents into all Western democracies. God knows what they’ve got in store for us.

We will need the very best of European intelligence to counter its moves and to capture as many ISIS agents as we can as they try to cross into European democracies. Again this won’t be a pleasant business but it’s vitally necessary. Confronting the challenge now engulfing Europe will not be for the fainthearted. Real courage that this country showed 75 years ago in confronting Nazi tyranny will have to be summoned up once again.

That courage must be mobilised and directed into battle if the fourfold immigration crisis which now threatens us as the months unfold is to be overwhelmed.

The existence of the Government is small beer compared to this country’s very stability, which is now under threat. It will need a degree of political determination by the Prime Minister which, so far, there has been no need for him to show.

As well as facing up to this fourfold challenge, Mr Cameron must also seize it as the unique opportunity to forge his leadership for the kind of Europe we need in the coming decades.

This Europe will be flexible, humane, outward looking and it needs to possess both the resolution and the resources to meet the needs of European nations in a fast changing world.

By giving Europe this lead more and more countries will realise the folly of maintaining the fortress Europe that the original founders envisaged. The centralised single European state with its clogged arteries and its other tell-tale signs of age, is not for Britain. We ought to have many partners in Europe who decide under the Prime Minister’s leadership that it is not for them either.