Little black dress: I love it, but I'm wearing a little blue one these days – Susan Dalgety

Time was when I would have at least one little black dress hanging in my wardrobe. Sadly, my frocks were more likely to be Marks and Spencer than Coco Chanel.

The little black dress is an enduring style icon (Picture: Shaun Curry/AFP via Getty Images)

But they proved to be the most useful items in my wardrobe. Throw on a set of imitation pearls and I could pretend to be Audrey Hepburn’s plumper, older sister. Dress it up with a black jacket and I had the perfect formal suit. And when a hangover struck mid-week – as they occasionally did – a black dress was the simplest wardrobe choice on those mornings when I could barely slurp down a black coffee.

These days I don’t have a single black dress. Instead, my go-to outfit is a plain LK Bennett frock, bought a few years ago in the sale. It skims over my curves, has three-quarter length sleeves and, gloriously, has pockets. I wear it whenever I have to look smart, from TV interviews to lunches with friends. But it is navy blue.

Years ago, I read in one of the fashion magazines I used to hoard, that black is terrible against ageing skin. I scoffed at first, but as the years progressed, I realised that the beauty experts were in fact correct. Navy blue is a much more forgiving colour for women of a certain age.

But there is nothing edgy about a little navy blue dress. It shrieks of matronly ladies sipping tea through pursed lips, whereas black is sophisticated glamour, with a hint of danger.

The National Museum of Scotland knows only too well the power of a little black dress. Its new exhibition, which was announced last week, will tell the story of how the garment – first made by Coco Chanel in 1926 – became the 20th century’s biggest fashion icon.

Beyond the Little Black Dress will, according to its curators, “explore how its complexities have made the little black dress simultaneously expressive of piety and perversion, respect and rebellion…”

Personally, I can’t wait to salivate over classic pieces by Dior and Jean Muir and marvel at what contemporary designers like Gareth Pugh and Virgil Abloh, who founded Off-White, are doing with a few metres of black cloth and a lot of imagination. But I will be wearing navy blue.