The backdrop was a Union flag, as big as they come.

The party manifesto offered was heavy with the glib, vote-grabbing promises that hint of desperation behind the scenes. Yet for David Cameron and his writers, neither of these was quite enough.

The Tory leader's speech on Tuesday drew on a distinct genre of British political rhetoric. Given the setting - a technical college in Swindon - it wasn't quite a Churchillian peroration, but there was a calculated attempt to echo those late-Edwardian cadences. The sub-text was clear: never mind the policies, feel the patriotism.

Here was Britain, once "an exemplary country"; "the small island with a massive impact"; "the bright light in the North Sea that has exceeded expectations decade after decade, century after century". Here was, or might again be, "this buccaneering, world-beating, can-do country". This was potted Tory history: the scepter'd archipelago; golden ages; and dark, inexplicable interludes.

Once mere policies were listed, Mr Cameron came to his point. He was in politics, he told the cameras, not for the glamour or the pomp, but for "people whose patriotism may be quiet but whose love for this country is deep and great". It was a love shared, and he would speak its name: "I am above all a patriot. I love my country with all my heart".

Some probably squirmed at that and recalled Dr Johnson's advice on the last refuge sought by scoundrels. Some might have noted the pragmatism: for Mr Cameron and his team, wrapping yourself in the flag couldn't miss. Some would have heard only routine, all-purpose chauvinism, the kind an American or a French president can turn on like a tap.

Still, the appeal was plain. Mr Cameron was presenting himself as a patriot who deserved the support of other patriots. He was casting his policies, even his career, in terms of unashamed nationalism. Those who recoil from the tendency can draw their own conclusions. Others will remember the David Cameron who fought for a No vote in last September's referendum.

Back then, he didn't spend much time acknowledging the fact that many of those supporting independence were not nationalists. Evidently that truth was impossible to grasp. Instead, he saw a question of loyalties, begging an (invited) audience in Aberdeen three days before the vote: "Please, please don't let anyone tell you that you can't be a proud Scot and a proud Brit. Please don't lose faith in what this country is - and what we can be."

It was hardly a rejection of nationalism. Instead, it was a defence of a competing British nationalism, the species celebrated last week in Swindon. Time and again last autumn Mr Cameron tried to rally No voters with declarations of love and patriotism. His cause was the 18th century invention he calls his country, not - or not for these purposes - one of the nations within it. But he was, as he remains, a nationalist attacking nationalists.

Interesting paradoxes hang on the fact. One is that authentic Scottish nationalists are badly placed to criticise when Mr Cameron exults over his island story. How could they? In generous theory, if not in political practice, all nationalisms enjoy equal rights. The Prime Minister gives his allegiance to the United Kingdom he likes to call Britain. Who has a right to deny him that?

Equally, however, this leader of Better Together was and is confused, like many who took his advice last September. One strand of their campaign was the claim that nothing good ever came from nationalism, that it is a dark, divisive and inherently nasty sentiment. This is true universally, apparently. Or true, at least, until a David Cameron claims an exception for that "bright light in the North Sea". British nationalism is different. Why and how?

The answers are interesting. They rest on the kind of claims that are otherwise used as accusations against Scotland's nationalists. In this telling, Britain is truly different, Britain is better, Britain is, for those who take its part, a special case. Mr Cameron will give you the list: the rule of law; a sense of fair play; parliamentary democracy; a rich and inclusive culture; and so on.

Isn't that what they all say, on every continent, in every era? Isn't claiming difference as a mark of distinction the kind of nationalist habit that repels Unionists? After all, down that road lies the belief that your unique, special little nation is superior. History says this is dangerous territory. Yet when Mr Cameron puts out the flags for his brand few fault him for anything worse than manipulative sentimentality.

There is nothing exactly new about British nationalism. What came to the surface in the referendum was a mass of contradictions. There was the argument for internationalism that still drew lines around one island group. There was the talk of "Britain's role in the world" that denied a role to others. There were those "lessons from history" showing nationalism leading always to fascism that never managed to explain how British patriots have, some of the time, escaped such a fate.

You could malign Mr Cameron's cause by mentioning Ukip, the BNP, or those Loyalists - according to them - who waved their Union flag and gave their Nazi salutes in Glasgow's George Square on the Friday night after the referendum. They call themselves patriots; they style themselves nationalists; they wanted the No vote for which the Prime Minister campaigned.

Better Together gave no encouragement, meanwhile, when the Orange Order staged a 15,000-strong march through Edinburgh to preserve the Union. That kind of support was not desired. But why not? It, too, was ostentatiously patriotic, vehemently - though the Order wouldn't care for the word - nationalist. The marchers were showing their pride in being British. Like Mr Cameron, they were declaring one kind of nationalism to be right and proper; another beyond, as it were, the pale.

There's nothing surprising about that. The Lodge will still be around, presumably, in the event of independence. You could say Mr Cameron treated his Swindon audience to a very selective sort of nationalism, one that omits much of the history of the British state, but that's customary. The proud past invoked by the Tory leader could be described as a continuous act of self-determination, but it often involved denying the right to others. No matter. Mr Cameron loves his country. He simply believes that his nationalism trumps all others.

Those who take his side pretend to be oblivious to what their loyalties mean, despite all the declarations, the flags and parades, the imperialist past and imperialist wars. Those who want to escape the contradictions would rather talk about the NHS. They all struggled to make their case during the referendum campaign, I think, because of what - unlike the Prime Minister - they could not dare to say. They too are nationalists.

Given the varieties on offer, anyone who fancies "speaking for Scotland" should meanwhile hesitate. It can't be done and it shouldn't be attempted unless you want to occupy the land of caricature where Mr Cameron's imagination roams. All you can do is decide that a nation exists and say what self-determination truly means.