In 1968, socialite Nan Kempner was turned away from Le Côte Basque in New York while wearing a YSL tuxedo. In defiance of the antiquated dress code, she removed the jacket and turned it into a skirt. Fifty years on, defiance is the attitude in tailoring once again, and designers are disregarding the rulebook. Or certain pages of it, anyway – fit, structure and cut are all prioritised, moderated by the same elegance demonstrated by Kempner that evening.

The asymmetric new cut seen at the AW19 shows of Dior, Brunello Cucinelli and Jacquemus will elicit double takes for its subtle transgression of traditional styles, with its single-breasted closure on a double-breasted construction. Block colours go big – see House of Holland’s fruity orange belted jacket and high-impact fuschia at Attico and Jacquemus – while checks are oversized to balance generous lapels.

The Row’s take is a slim-cut, understated staple, and while we like the extra length in the torso of Anna Quan’s Sienna jacket (a street style highlight at Copenhagen Fashion Week in August), we recommend having the sleeves shortened by your tailor for the perfect fit. As with the best tailoring, the trend is unisex – Naomi Campbell wore Kim Jones’ interpretation at the Dior Homme SS19 show in Paris, where male models wore it down the catwalk with plimsolls.

Embellished checked woven blazer, Tibi, £895, net-a-porter.com

Ciel wool-blend crepe blazer, The Row, £2,260, net-a-porter.com

Sienna jacket, Anna Quan, £365, annaquan.com

Orange wool-blend belted jacket, £550, houseofholland.co.uk

Checked wool blazer, Brunello Cucinelli, £3,650, net-a-porter.com

Crepe silk blazer with detachable sequin cuffs, £3,460, shop.brunellocucinelli.com

Fuschia wool-blend gabardine blazer, Attico, £840, net-a-porter.com

Sienna jacket, Anna Quan, £365, annaquan.com

Grey blazer, £850, Acne, acnestudios.com