Known in Scotland as "Her Royal Highness The Countess of Strathearn", Catherine (and William, of course, although I can't quite picture him in a kilt!) has her own tartan in shades of red, gold and deep forest green:
Kinloch Anderson, Royal Warrant Holders as tailors and kiltmakers to the Queen, the Duke of Edinurgh and the Prince of Wales (known in Scotland as the Duke of Rothesay), state on their website that the Strathearn tartan was most likely adopted by Queen Victoria's father, the Duke of Kent, who was Colonel of he Royal Scots between 1801 and 1821. The name Strathearn is derived from the old Stewartry of Strathearn in Perthshire, central Scotland. The Strathearn title has long been connected with the Royal Family: apart from Queen Victoria's father, who held the double dukedom of Kent and Strathearn, there were Prince Henry, a son of Frederick, Prince of Wales, who was created Duke of Cumberland and Strathearn in 1766, and Queen Victoria's third son, Prince Arthur, who was created Duke of Connaught and Strathearn in 1874.
Catherine debuted a silk scarf in her tartan at the Diamond Jubilee River Pageant on 3 June 2012:
It is a product by Scotweb Tartan Mill, handmade in Scotland using the finest pure spun silk. Catherine's is in the Strathearn No.2 Modern tartan, with the brand's exclusive hand-knotted five-knot fringe detail. The scarf is available in wide choice of tartans and priced at £295/€420/$385; there's usually a waiting time of 4 to 6 weeks for it.
If you're after a cheaper repli-kate (who isn't?), Scotweb offers the same scarf in pure new wool, priced at £85/€120/$110 and aptly named the Kate Middleton Scarf. Measurements are exactly the same, although apparently the distinctive hand-knotted fringe motif is no longer available on this style.
From Scotweb: "Woven at the same artisanal mill in the Scottish Borders, this version is produced in fine wool rather than silk - so you can get the look, but at a fraction of the price. It's extra-long too, just like hers". Even better, the new wool option is in stock at time of writing, and ready to ship.
The scarf is really soft, despite being made of pure new wool, which I find tends to be prickly. My scarf has no care label, but even without one, there's no doubt this is an item that requires professional dry cleaning, or you'll risk ruining the fringing.
The Duchess has subsequently worn (or carried) the scarf at Prince William's appointment as a Knight of the Order of the Thistle in Edinburgh on 5 July 2012...
On another Scottish trip, this time in May 2014, the couple were presented with a giant teddy bear wearing a Stathearn tartan kilt as a gift to Prince George:
Of course Catherine has worn other tartans over the years, as well as the Strathearn tartan. During the April 2013 visit to Scotland she debuted the "Workers" coat by Moloh, in shades of navy and grey (the style has been revamped in navy and black damask for A/W 2015):
The coat was repeated for church at Balmoral in September 2013:
The Black Watch coat by Alexander McQueen has been worn twice so far, too - the first time on a visit to her former prep school, St Andrew's in Pangbourne, Berkshire, in November 2012, just before her first pregnancy was announced...
...then again on Christmas Day the following year:
This remains one of my favourite-ever coats of hers, and I do hope we'll see it again some day!
Incidentally, the blanket placed in the carriage that brought William and Kate back from Westminster Abbey after their wedding to ward off any potential chills was in the Black Watch tartan, as shown in the aerial photograph below:
Additionally, there's the cashmere-mix tartan wrap in claret by Really Wild Clothing, which was first worn for the early morning church service at Christmas 2013 (below left) and later at a friend's wedding in December 2014 (below right):
Quickly restocked after initially (unsurprisingly) selling out, the wrap seems to have been included in the permanent Really Wild catalogue and remains available at £135/€175/$196 plus shipping. Described as a "luxury Scottish cashmere mix wool wrap in a warm tartan consisting of claret and navy checks", it measures a very generous 216 x 70 cm, including a short fringe. While the cashmere content is minimal (just 5%), it gives a pleasantly soft feel to the wrap, making it a great choice for those first autumn chills (admittedly, a long way away now we're heading into summer, but it pays to be prepared!).