IF I had a vote in the Tory leadership election, I would cast it for Rory Stewart, MP for Penrith and the Border and the newly-appointed Secretary of State for International Development.

He is a Scot, for one thing, though born in Hong Kong – not in itself, of course, a disqualification. Better than that, he boasted a home address in Perthshire before he got mixed up in politics. His constituency has a tradition of choosing its MP from the northern side of the border it is bounded by – before him, it sought out Willie Whitelaw and then David Maclean. Rory highly approves because he claims a loyalty to something called Middleland, which I’ll come back to.

WATCH: Ruth Davidson dodges question on her election failure

I’ve met him a few times in front of the microphones in chat shows and book festivals. At our first encounter he looked to me about 19 years old – he was actually over 40 – but public responsibility seems to be ageing him. Despite that, he retains an easy charm, which is one of the things bought by an education at Eton (not that every Etonian acquires it), so we were on first-name terms from the start.

Current events are confirming there is more to him than a boyish grin. He has reached the cabinet after just nine years at Westminster, showing along the way a praiseworthy independence of mind. Last August, after he had become the junior minister for prisons in England, he said he would resign at the end of a year unless he brought about a measurable improvement in their condition. Early promotion has relieved him of the need to keep that promise, but his initial intervention in the leadership contest again reveals some steel otherwise shrouded by the free and easy manner.

The first edginess in the contest came from Rory’s avowal that he would not serve in any government under Boris Johnson, who as things stand is the bookies’ favourite to win. I hope it brought home to the other candidates that only by somehow banding together (though there are already too many of them) could they stop Boris taking one of the top two positions in the parliamentary ballots. After that the whole business is thrown open to the decrepit and reactionary membership in the Conservative associations round the country, with a result that appears inevitable. Rory has, however, not only a ploy but also a principle in mind.

READ MORE: Stirling Tories are taking the EU election result REALLY badly

He recalls Boris had recently denied to him any interest in a no-deal Brexit: “We had a conversation of about 20 or 25 minutes and I left the room reassured by him that he wouldn’t do this. But, it now seems that he is coming out for a no-deal Brexit.”

Recalling that a majority at Westminster has voted down no deal, Rory adds: “I think it would be a huge mistake. Damaging, unnecessary, and I think also dishonest.”

A logical conclusion follows: “I could not serve in a government whose policy was to push this country into a no-deal Brexit. I could not serve with Boris Johnson.”

There we have it. In their conversation Boris said, as ever, what he thinks his audience wants to hear, even if it’s only one man. It need not bear any relation to what Boris will actually do, since the two things are not connected in his mind either. Yet here is the foremost contender to be the UK’s next Prime Minister.

Unfortunately, I don’t think Rory will be left the last man standing against him. Surely today’s Tory party could not have a final run-off between two Old Etonians … could it? But at least Rory will be able to leave his calling card this time and live to fight another day.

Meanwhile, I would like to direct readers’ attention to his website, a rich collection of material revealing a man interested as much in nature, history and literature as in politics, and so most unusual among the type of one-dimensional narcissists we get as MPs today. It contains his best parliamentary speech, in praise of the hedgehog. It offers also a memoir of his father, who had been the UK’s chief spook in Hong Kong: “His fiercest identification was with his Highland regiment, the Black Watch, with which he fought in the war. He was an extreme Scottish extrovert, swathed in tartan, serving haggis aggressively to his English guests, while remaining a fervent believer in the Union.”

The National: Boris Johnson remains the favourite in the Tory leadership raceBoris Johnson remains the favourite in the Tory leadership race

That kind of Unionist nationalism, as historians call it, was common a century ago but today has largely dissolved into its constituent parts. Rory, perhaps conscious he is one of its last representatives, has tried to give it more concrete form. Before the referendum campaign of 2014 he launched a project to build a cairn near Gretna, where members of the public could lay a stone to mark their support for the Union. About 100,000 did so.

At the same time, he prepared a documentary television series for the BBC on the history of what he called “Britain’s Lost Middleland”. It pointed out that in the past the people of the Scottish Borders and of the northern English counties led much the same sort of lives. They eked out an existence in pastoral poverty which was all the same enriched by legend, song and a taste for personal ornament, all against the marvellous scenic backdrop. If it had not been for the pesky Romans, dividing this rude idyll with the construction of Hadrian’s Wall, the cultural unity might have continued as the best basis for future political unity as well.

A beguiling thesis but a wrong one, I think. The biggest boost to the borderline came from English aggression after the Norman Conquest of 1066. It led on through time to the most centralised state in Europe, based in London but seriously intent on extending its uniform control over the whole British Isles.

Except that, in epochs of limited technology, it at length came up against barriers it could not surmount, one of them that rough country of Middleland. It had to rest content, therefore, with drawing a line between Carlisle and Berwick, beyond which the Scots continued to indulge delight in being different. It’s a pattern still recognisable today.

WATCH: Gove says Scots are seen as 'unattractive creatures' in unearthed TV clip

The distinction has stood the test of time. It was written into the Union of 1707 because the alternative would only have been more war between the two nations. It has survived over three centuries of a UK where centralising measures grew steadily more intense, finally in the 20th century pushed alike by the Labour and the Conservative parties. Yet today we see, with both those parties now at risk of dissolution, that the distinction between Scotland and England endures as the most decisive determinant of relations between them.

The next time I see Rory Stewart I’ll try to persuade him of this. One of the best things to be said of him is that he cares about the outcome of the argument, cares about Scotland in other words. It is more than can be said of Boris Johnson or the rest of the rivals for the poisoned chalice that the blimpish crones of their membership will hand them.