The Ministry of Defence is like a sauna on Sunday. The air circulation system has been switched off and the place is hot — and deserted. Yet when you reach the Secretary of State’s floor, a small team is hard at work. As you enter Michael Fallon’s office, you see why. On an easel sits a map of Iraq and Syria. Tellingly, though, this isn’t the only map on the stand. Sitting behind it are ones of Pakistan, the Central African Republic and Sierra Leone. It emerges later that the one of Ukraine has gone missing.

Fallon is 62, but he has the energy of a man half his age. Our conversation is punctuated with regular requests from him to his staff to bring him a map, a copy of the Nato charter or some other piece of paper. Having finally joined the cabinet 21 years after he entered Parliament, he is determined to make full use of this late flowering of his political career.

Unlike many modern politicians, Fallon doesn’t speak in some Westminster code but plain English. He warns that Islamic State is ‘a clear and present danger to us… and we have to do something about it’.

He doesn’t accept that this is ‘some side effect of the previous intervention’, dismissing the whole idea that this is blowback from the Iraq war with a wave of the hand. He has little time too for the idea that Britain should stay out of the fight. He seems morally offended at the suggestion that we should leave it to other countries to deal with Islamic State, and irritated at the failure of some to grasp that the struggle against Islamist extremism is ‘Britain’s business’. ‘We’ve had attacks on the streets of London, on our transport system, at Glasgow airport, the murder of Lee Rigby — how much more evidence do you need that this is a very clear and dangerous threat to our way of life and to all the democracies of the West? This is a new battle of Britain.’

But Fallon accepts that there will have to be a vote and debate in Parliament before Britain joins this fight. He says, ‘I hope Parliament now will have the courage shown by our armed forces already, will have the mental strength you saw at the Invictus Games, to take on this challenge, but we’ll see.’ One wonders how wavering MPs might react to this emotionally loaded appeal.

Until now, it had been assumed that British military activity would be confined to Iraq. The country’s government is already requesting assistance against ISIL. As Fallon explains, ‘Everything we’ve done inside Iraq so far, every single flight, and I authorise each flight, each night — whether it is humanitarian or supplies, every single flight is done with the permission of or at the invitation of the Iraqi government. So we have all the authority we need to operate in Iraq, because we’re doing so at the request of the legitimate government of Iraq.’

But Fallon then outlines the case for extending British participation to Syria: ‘The government of Iraq is also entitled to argue that it is under attack from ISIL forces in Syria or coming from Syria.’ Three times Fallon makes the same argument: ‘Iraq is under attack not just from terrorists inside its own borders but… from terrorists in the north of Syria, and if Syria continues to be unwilling or unable to deal with ISIL, then at least the question arises as to whether we shouldn’t assist Iraq in doing so.’ With the US-led co-alition already striking sites in Syria, it seems that this will be the British justification for joining these bombing raids.

Fallon, though, warns that we shouldn’t just see ISIL as a Middle Eastern problem. ‘It is popping up all over the place,’ he says, ‘in West Africa, into southern Libya, into the supply routes through Libya to the southern side of Europe. ISIL is now present in Indonesia. It is something that affects a much wider area than just Syria and Iraq.’

It is not just the so-called Islamic State that worries the Defence Secretary. He is also concerned about Russia and Vladimir Putin’s ambitions. He says that Putin has embarked on ‘a deliberate strategy to recapture some of the old border areas of the Soviet Union’. He wants ‘larger and continuous Nato-led exercises on the eastern flank to deter Putin’.

Fallon is emphatic that Article 5 means  if Putin attempted what he has done in Ukraine in any Nato state, Britain would have to intervene. ‘We shouldn’t be ambiguous,’ he says.

In the current global climate, it seems obvious that Britain will have to spend at least 2 per cent of GDP a year on defence. So I ask Fallon if the government will back legislation for this, as it is doing for the 0.7 per cent target for international development spending. Fallon sidesteps the question. I then put it to him that the Conservatives should at least put it in their manifesto as a commitment. ‘What goes in the manifesto?  Well, wait and see. We’re working on that at the moment,’ he replies. This is a heavy hint that the Conservatives will commit to 2 per cent. Fallon, though, declines my invitation to say that he would resign his post if defence spending ever falls below that level.

The aid and defence budgets should be seen as parts of the same whole, he argues. ‘The biggest problem we are facing now, in Libya, in Liberia, even in Nigeria where they have lost control of the northern province, in Sudan, in Yemen, right across these countries, is that these states are starting to fail and that’s where in the end — sadly — you end up having to intervene with armed force. So these aren’t opposites. Justine Greening’s budget and mine you should add together, they are security budgets.’

Fallon is bullish about the Conservatives’ election prospects. ‘Britain is trusted again,’ he says. ‘The economy is booming, unemployment falls and falls in my constituency, and with a lot of reform as well. Mrs Thatcher never reformed the welfare state or secured as much educational choice as we’ve done in just four years. She didn’t do that in 11 years.’ That a politically experienced cabinet minister is prepared to talk of a boom without adding any caveats is a sign of how confident the Conservatives now are about the recovery.

Having worked with both Thatcher and Cameron, Fallon is well placed to compare the two. When I invite him to, he pauses before saying, ‘Each prime minister is different, they are different personalities. Margaret Thatcher was fairly terrifying and David Cameron doesn’t work by terrifying people.’

Fallon has the ideological confidence of a Conservative politician who came of age under Thatcher; he has no hesitation in agreeing that Britain is an overtaxed country. In this uncertain world, the country might find it reassuring to have a Defence Secretary with such firm views. ​