One of her eureka moments when she had to dress for public inspection, Samantha Cameron told me last week on stage at the Telegraph’s Women Mean Business Live conference, was learning to avoid creases. It’s a good lesson: either make sure there’s a steamer handy, practise sitting so that you don’t get those awful horizontal folds across your thighs (this involves not really sitting at all) or, find a bomb-proof fabric. The latter has become a cornerstone of Cefinn, Cameron’s fashion line “for multitasking urban women,” which she launched after leaving No 10. That crinkly triacetate has become one of Cefinn’s most recognisable features and a reason why her flattering, gently fitted blouses and dresses have become a professional woman’s favourite.

It’s the seemingly small details on which foundations of self-confidence are constructed (having a good nude bra to hand and comfortable heels are her other top tips) and which are more important, it turns out, than outmoded ideas about shoulder pads or not wearing florals. Florals (the right ones, on a dark background) are fine in almost any situation.

Another workwear label that should be on your radar is Dai. Its tailoring is sharp, but the selling point is its stretchy washable fabrics which are so forgiving you could, if you wanted, do yoga in them. White plane-to-boardroom jacket? No problem. Its American-expat founder and CEO Joanna Dai, a computer and electrical engineering graduate from Cornell University, is a walking template of cool, soft power.

Along with the minutiae, the bigger picture matters, too. A day after Cameron’s talk, Clarissa Farr, the former High Mistress of St Paul’s Girls’ School, was on another stage, confessing that she used to go out of her way to avoid dressing like “a harridan headmistress.”

Farr was talking at an event in Fenwick of Bond Street organised by designer Edeline Lee. Some of us have always enjoyed the intersection of beauty and brains, but for others, seeing the former head so at ease among the winter collections was novel. We can probably all agree that having a designer of elegant, polished, ladylike clothes pushing for intelligent discourse among the clothes rails is progress. As Lee says, “Fashion designers often speak of powerful women, yet so often show our work on young silent girls.”

Joanna Dai, Founder and CEO of Dai​ wears Trail Blazer Ivory, £95, Dai; Pretty Pleat Top Ivory Silk, £145, Dai

Farr was keenly aware of the power of clothes to communicate. “Women have so many more choices than men in what they can wear. That’s a plus and an advantage. We’re bombarded with more images of the idealised female in a single day than our grandmothers were in a lifetime.”

It’s not surprising, she says, that we have a problem with how we view female power. “Remember those caricatures of Theresa May with her big shoulders and beaky nose?”

And yes, Farr confessed, she did reject one of the dresses she was lent on the grounds that it was “too schoolmarmy”.

Farr also suggested that we need to redefine what modern masculinity looks like, too – the first time I’ve heard a school head subscribe to the Gucci theory. Her fellow guest speaker, the financier and mother of nine Dame Helena Morrissey, was on board. An outspoken campaigner for equal gender pay, Morrissey has strong views on what she calls “the old trappings of power dressing. A lot of women feel pressure to conform to outdated notions of power and that includes the way they dress.”

Their message is that we should embrace all the choices out there. As Morrissey says, “There’s no point in diversity if you still feel pressurised to be the same as everyone else.”