From his grand country house in Gascony, the Vote Leave champion tells why no cost is too great to achieve Britain’s exit from the European Union – not the EU’s total collapse, nor David’s Cameron’s job

The journey from London to a remote corner of south-west France takes long enough for the thought to occur, more than once, that it is an unlikely location for a Brexit HQ. The man who hopes to lead us out of Europe lives alone in an extremely handsome country house – not quite a chateau, but several notches up from a maison – deep in rural Gascony. The pristine period chic of its reception rooms is flawlessly French, and unless you study its library shelves, which groan with British political tomes, or use the downstairs loo lined with framed and signed photographs of Downing Street cabinets, you would never guess who lived here. As his former boss once famously observed, it is a funny old world.

The impression of improbability is compounded by Nigel Lawson’s expression as he receives me. It is one a courteous but very private gentleman might wear to greet someone who had broken down in his elegant driveway. Nothing about his bearing suggests a man bursting to make the case for changing the course of his country’s future. It seems to say something more like: “Well, you’d better come in while you wait for the RAC.”

I’m not sure he smiles once during the 90 minutes we spend sitting opposite each other on formal chairs. I think I detect an occasional hint of a more mischievous side, but the austerity of his magnificent grandeur leaves little room for warmth. I’m afraid I might have inadvertently offended him in the first few minutes, when I reflect on the surprise of his return, at 83, to the heart of British politics. “I’ve not been as inactive as you would imply,” he corrects me. “In 1999 I founded a thinktank on climate change, of which I am a very active chairman. Which meant I was probably slightly more active than most people my age.” But to those of my generation and older, he will always be a man from the 1980s, Margaret Thatcher’s chancellor. To those younger, he is probably the maverick climate change sceptic, or possibly just Nigella’s dad.

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Except that, in February, he was appointed chair of the Vote Leave campaign. It was only ever meant to be an interim position, and last month he was succeeded by Gisela Stuart – but he remains a highly active member of the campaign committee, and will be devoting the next three months to what he considers the defining political cause of our age, if not his lifetime.

His appointment was intended to steady the Brexit ship, rocked by infighting between Vote Leave and the rival, Ukip-based group, Leave.eu. At the time, Leave.eu’s spokesman publicly urged Lord Lawson to “pick up the phone as soon as possible, so we can finally come together and fight this referendum as a single united front”.

But it transpires that Lawson has not even spoken to Leave.eu, let alone co-ordinated tactics or contemplated a merger. “It’s not realistic,” he says loftily. “I think we have to make our case, and the other group – Nigel Farage, Ukip – make their case.” What is his impression of Farage? “Oh, I’ve never met him.” Pressed for an opinion on Ukip’s leader, Lawson offers: “He appeals to a different segment of the population.”

The referendum could not matter more to Lawson, but his manner is less that of a passionate campaigner than retired don. On most of the issues exercising the campaign, he is supremely off-hand to the point of dismissive; on the vexed question of the UK’s trading relationship with the EU, post-Brexit, he affects airy indifference. “Would we leave the single market? We-ell,” he reflects, “the ‘single market’ is a curious term,” as though this were an esoteric matter of semantics. He thinks we would probably be able to negotiate a free-trade deal with the EU, “because we are Germany’s most important market”. Gus O’Donnell warned this week about the grave risk of protracted uncertainty, but when I ask how long these negotiations would take, Lawson gives a vague, careless shrug. “Oh, doesn’t really matter.”

Facebook Twitter Pinterest Lawson with his daughter Nigella in 2008. Photograph: Dave M Benett/Getty Images

Many of his arguments sound like lines that appeal to people who already agree with him. Asked to clarify what sort of future we would be voting for if we backed Brexit, he says: “Look, most of the world is not in the European Union.” How persuasive this will be to the unconverted isn’t clear, and when I press him for details he becomes impatient. “Look,” he demands sharply, “what do you think the weighted average is of the common external tariff? What do you think it is?” I suspect he only asks the question to try to expose my ignorance. “Yes, that’s right,” he agrees, when I suggest 3%. “Well, it’s trivial, anyway.” He is confident that prices won’t go up, even if we have to pay that tariff, because we will be free to negotiate better trade deals with the rest of the world. I ask how he can be so confident. “Well, Switzerland has done that, so why shouldn’t we?”

In Lawson’s defence, the remain campaign can seem just as oddly relaxed about making its case to the undecided. Earlier this week, I contacted an aide to Alan Johnson, asking to speak to the chair of Labour In about Lawson prior to the interview. It was a self-explanatory opportunity for Johnson to challenge some of the leave campaign’s positions. The aide texted back wondering if I could be more specific about why I wanted to talk to him. I think I can safely say I have encountered more energetic parish councils.

In fairness to all camps, they share the same difficulty. What is it that will actually change people’s minds? Will Straw, leader of the cross-party Stronger In, is a livelier campaigner, and says it’s the hard data of economic facts that will gain traction – but the woman next to me on the plane to Toulouse just laughs at this. “Nobody cares about facts! This isn’t about facts, it’s about emotions.” Lawson thinks it is very difficult to know. “I don’t think you can make a generalisation about what the British people think is most important.”

For Lawson, the answer is simple. Brexit is not about border controls or immigration, “important though they are”. It is certainly not about being anti-Europe. “I love Europe! That’s why I live in France.” It isn’t even about economics, although he has no doubt that “we’d be far better off out, economically. To suggest that the European Union is an economic success – well, it clearly isn’t. Look at unemployment rates around the EU, particularly very high youth unemployment rates. So the idea that somehow it’s an economic asset to us to be in the EU is, I think, bizarre. The EU has never made economic sense.”

Facebook Twitter Pinterest With Margaret Thatcher in the 1980s. Photograph: Manchester Daily Express/SSPL via Getty Images

One simple reason justifies Brexit for Lawson. “The important issue is democracy and self-government. It is about that principle. Self government is more important than anything else.”

It may be because the supremacy of this principle is so self-evident to Lawson that he can seem detached from voters more preoccupied with issues such as keeping their jobs. The purity of Lawson’s commitment to the principle is a wonder to behold. Conservative colleagues including Philip Hammond and William Hague have issued quasi-apocalyptic warnings that Brexit could trigger the collapse of the EU. But if that were to happen, Lawson says casually, it would be no bad thing at all.

“No, it would be good for the countries of Europe. When you have an entity with a really serious democratic deficit, and proving to be an economic poor performer, the idea that there is anything to be lost if it breaks up peacefully I find totally unconvincing.” Lots of people would describe it as a historic catastrophe. “No, well, they’re completely mistaken. I cannot see any rational case for believing that. Things don’t go on for ever.”

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If Lawson had his way, would he abolish the EU altogether? “You could say that once upon a time it served a useful purpose, in confining Germany. You could make that case – and I really bought into this in the 50s. But it’s passed its sell-by date: it’s served its purpose. I see no purpose in the EU now at all. I think that if it ceases to exist we’ll have better relationships. If you look now, there is far more hostility among the different countries of Europe than there has been at any time since the war. The great majority of people in Europe do not want to be part of a political union.”

Is he sure about that? “Well, that would be true of the French people. I mean, it’s not true in Luxembourg, of course. The little countries, they have a slightly different perspective.” He chortles. “I mean, Luxembourg is very little indeed. About the same size as Croydon.” So dissolution of the EU would be a price worth paying for British sovereignty? “That would be no price to be paid at all.”

Facebook Twitter Pinterest Photograph: Ulrich Lebeuf/MYOP for the Guardian

He is similarly untroubled by the possibility that the union might be the price the UK pays for Brexit. “There’s no connection. No connection whatsoever.” People are quite wrong, he insists, to worry that Scotland might leave the UK if it votes to remain while England votes to leave. “The decision to hold another Scottish referendum is the decision of the British government, it’s not for the Scottish government to decide.”

Others worry that the price would be Tory party unity, but Lawson dismisses this briskly. “I don’t see things in those terms. What matters is the best interests of the people of Britain. The press always loves to talk about personalities and careers, because it’s more entertaining and easier to grasp than some of these bigger arguments.”

Is a David Cameron’s premiership a price worth paying for Brexit? “He’s already said he’s going to stand down.” Lawson sees no reason why a vote to leave should precipitate the PM’s immediate departure. “In fact, I think in a sense he has a duty, he and his cabinet, to stay and implement the people’s verdict in the most effective way.” He refuses to be drawn on relations between Downing Street and leave campaigners in his party, or comment on the leadership prospects of Cameron’s potential successors. “I’m sorry to be very boring, but whether we should leave the European Union or not is something of such fundamental importance, it trumps everything else.”

Lawson glances at his watch. He is going out for dinner in a bit with his girlfriend. His last girlfriend was 40 years younger than him, and lived in Oxford, whereas this one is local and only 10 years younger, which he is finding much easier. “So I’m very happy with her.”

And is he happy with how the campaign is going? “Oh, I’m too close to be able to judge.” He has previously predicted that Britain will vote to remain, but says now: “I have no idea how it’s going to work out. I think it’s extremely difficult to predict. All I was pointing to is that history tells us that the great majority of referenda support the status quo. But that doesn’t mean it’s unwinnable. And I think there are a lot who haven’t made up their mind. It’s also very early days. I mean there’s another, what is it, three months? So there’s a lot of campaigning still to be done.”

Three months doesn’t strike me as very long, given what is at stake. I ask what we can expect from Vote Leave. “Oh, you’ll see,” he says, seeing me to the door. Will they be unveiling surprise supporters? Unearthing killer facts?

“Oh, it’s a whole lot of things. But you will see. You will see.”

• This article was amended on 4 April 2016. A picture caption on an earlier version incorrectly attributed a quote to Nigel Lawson.