Get your kilts, bagpipes and haggis ready to celebrate the heritage of the Highlands.

Even before the dawn of social media, fashion news travelled fast. Back in the 1950s, the Duke of Windsor wore a suit in a distinct pattern to a dinner near his home in Antibes. Subsequently, “one of our guests mentioned the fact to a friend in the men’s fashion trade, who immediately cabled the news to America,” the Duke noted in his book A Family Album. “Within a few months [the pattern] had become a popular material for every sort of masculine garment, from dinner jackets and cummerbunds to swimming trunks and beach shorts.”

Remarkably, that patterned cloth was tartan – the stuff of kilts, country clubs and the occasional table cloth. Yes, it crops up on trims and in linings – see Burberry trenches, Barbour jackets and Baracuta raincoats. And on the occasional tie, sock or work shirt, where it might be referred to as plaid. But for most people, it is indelibly connected to Scotland.

Certainly, tartan’s connection with the Highlands is undeniable, but that isn’t the beginning and end of the matter. “That’s more historic,” says Mr Nick Fiddes, the managing director of Selkirk’s DC Dalgliesh. “A third of our customers have no particular interest in Scottish heritage at all.” The last surviving mill in Scotland, DC Dalgliesh specialises in making hand-crafted tartan cloths and is, arguably, responsible for bringing tartan into the 21st century through its designs and collaborations.

It was DC Dalgliesh that designed the tartans used in Pixar’s Brave, the Gleneagles Hotel and the uniforms for Canada’s Westjet airline. Messrs Neil Armstrong, Nelson Mandela, the Dalai Lama and even Google all have their own tartan. None of them are Scottish. The Queen isn’t really either, of course, but you’d still be breaking the rules if you were to wear her Balmoral tartan, unless, that is, you happen to be her personal piper.

“Tartan is the kind of pattern that tells people who you are from 50 paces. It’s a form of visual communication,” suggests Mr Fiddes. “But there’s a broader appeal to it than its Scottishness, and for many that’s because it’s a pattern of almost infinite variety, from the in-your-face to the subtly detailed.”

Tartan is not just a checked assemblage of a few core colours. Because the colours are blended at different points on the cloth, it’s endlessly interesting for those with a good eye. But it’s also why the most successful tartans tend to use just three to five base colours, with those that use many more tending to, as Mr Fiddes puts it, “slide into confusion, ending up with too many elements to look at”. There’s an actual mathematical formula for the right combination, though DC Dalgleish has fun working other patterns – the Fibonacci series, for example – into its tartans.

DC Dalgliesh alone has some 45,000 different varieties on its books, with new tartans being registered every week. Every plaid is not a tartan, though. “Plaid is a criss-cross pattern, whereas tartan is a criss-cross pattern with a name,” Mr Fiddes says. Traditionally associated with a particular people or place, each tartan must be recorded with The Scottish Register of Tartans, an organisation launched by the Scottish Parliament just 10 years ago.

Further back than that, however, the Dress Act of 1746 actually prohibited the wearing of tartan, stating that doing so was an act of rebellion. This followed several Jacobite revolutionaries donning it in response to the acts of union between Scotland and England. The inhabitants of different regions of Scotland only started to wear different tartans as a means of identification in the early 19th century after the law was repealed in 1782.

Indeed, you may have to consult the register to find out if you’re wearing a tartan or merely a plaid, but of late the likes of Berluti, Gucci, Dries Van Noten and Ralph Lauren are all getting in on the action of the criss-cross style. If you want to play it safe, stick with a scarf from Johnstons of Elgin. After all, if anyone knows a thing or two about tartan, it’s a brand that has been based on the banks of the River Lossie for the past 222 years. It doesn’t get more Scottish than that.

Shop what to wear here