Appropriately enough for a conversation about his new diffusion line Hart Hollywood, Nick Hart just got back from his annual January sojourn in Los Angeles. To coincide with the Golden Globes, the founder of scalpel-sharp tailoring brand Spencer Hart – named after Hart’s son – set up shop in a bungalow at the Chateau Marmont, the infamous celebrity haunt. There, he outfitted an eclectic cast for the awards: everyone from Homeland actor Damian Lewis to Game of Thrones writer and producer Dan Weiss via Vampire Weekend frontman Ezra Koenig. Although Hart is by now acclimatised to such starry surroundings, the odd moment of surreality still ensues.

“We were having a viewing party for the Globes, playing music when the adverts were on, including lots of Bowie,” says Hart. “Then the news broke about him dying. I went out to the garden to have a slightly quieter time and saw an acquaintance of mine, so I said, ‘Have you heard?’ I suddenly realised that she was sitting with Kiefer Sutherland, who is a long-standing Spencer Hart client and was actually wearing one of our suits: he shops in our Brook Street store when he’s staying at Claridge’s and filming over here.” Hart had never met Sutherland before, but they soon got to talking: “He recorded a message on my friend’s voicemail so when you call it, Jack Bauer picks up.”

The Chateau is notorious for excess, whether it’s funny man John Belushi overdosing in one of those bungalows, Led Zeppelin drummer John Bonham riding a Harley-Davidson through the lobby or Britney Spears being banned for smearing food on her face. Hart, however, is better known for restraint: his stylistic signature is a slick, dark suit in any colour – as long as it’s black or maybe midnight blue – with a fitted white shirt and a slim or ‘air’ tie.

“I suppose the aesthetic is ‘less is more’,” he says. The monochromatic thing, meanwhile, happened almost by accident. “When I started Spencer Hart, the thing that influenced me by far the most was bebop musicians in the late 1950s,” he says. “It just so happened that they were photographed mainly in black and white.” That also explains why Hart’s distinctive riff on classic tailoring has resonated with recording artists from Alex Turner to Bowie Himself.

As well as being inspired by the much-celebrated ensembles of the Rat Pack, Hart’s minimalism has its foundations in modernism. “If you go right back to architecture in Palm Springs in the 1940s, architects, musicians, creative people in general, have always taken classic things and subverted them,” he says. “The idea of wearing a very traditional white shirt, but without a tie, buttoned up to the neck, under a clean black suit, and maybe the lapel on the suit is very narrow, and the trousers are a little bit shorter… It’s just giving those things a slight edge.”

While his aesthetic is predominantly monochrome, it’s by no means one note. “We try to work in quite narrow parameters but create as much drama within them as possible,” he says. “For instance, playing on a white shirt by adding marcella [a cotton fabric similar to piqué] or pleated detailing but in a different way, or combining different fabrics.”

Those unshakable parameters – dark suit, white shirt – provide a rock-solid base on which to build a few flourishes, without the overall construction becoming too overwrought: “I’ve always been nervous of things appearing to try too hard.”

That DNA has been inherited by Hart Hollywood. Available online at ASOS and priced as sharply as it is cut, the little brother is more accessible in several respects than its older, high-end sibling, which offers made-to-measure or bespoke in a converted bank vault at its Mayfair flagship.

“I wanted to get to a much wider and younger audience,” says Hart. “Online, at places like ASOS, is the way people shop today. Even in just the last five years, the way we consume information – and actually buy things – has changed completely.”

One quick glance through the range though will tell you that Hart’s tastes haven’t changed, as evinced by his favourite pieces in the collection. “I really love the white collarless shirt with a marcella bib front and cuff, with a little HH embroidery,” he says. “When we were in LA, lots of people took that shirt. I also like the dark blue suit with narrow notch lapel and waistcoat. It’s a real signature piece of ours. But again it looks quite timeless. They’re pieces I wear myself.” The classics always get played.

Although Hart’s reference points might be 50 years out of date, his clothes continue to look remarkably contemporary, thanks to their slimness and styling touches like that air tie or collarless shirt. But a dark suit or white shirt is never really going to go out of fashion, partly because they’re never really in fashion either – much like Hart himself. While trends come, go and come again, he’s found a signature style that works for him season in, season out.

“Different things suit different body shapes,” he says. “If you’re a big guy, you want unstructured jackets that soften you. I’m a bit lanky, so I look better with a semi-constructed shoulder.” Trial and error can thus be kept to a minimum – as long as you’re honest with yourself. “I remember when Prada menswear launched: all these beautiful, unstructured jackets,” says Hart. “It was all too short on me and the shape didn’t do me any favours. But I wanted it so much that I bought it anyway.”

The paramount importance of fit in tailoring is another aspect that never alters. “The shoulder is the number one thing,” says Hart, not least because it can’t be altered without great difficulty and expense. “If you had all the money in the world, you could go to a great tailor but come out with something that really doesn’t suit you,” he adds. “Tailors, especially famous Savile Row ones, tend to specialise in a very specific house look. That will work on probably 50-60 per cent of people and not on others.”

Hart himself specialises in what you might call cocktail attire, that category that sits somewhere in between business attire and black tie. But what are the rest of us, who don’t share his expertise in party outfit planning, doing wrong?

“I think people try too hard,” says Hart. “But things are improving because people now have so much more information about menswear than they did a few years ago.” (You’re welcome.) And while dress codes and fashion trends will be drummed into us, ultimately style is dancing to your own tune. “One shouldn’t be dressing to please others, or fit into the social norms,” he says. “The best kind of dressing is when you’re doing it for the sheer enjoyment, like eating good food. That’s what it’s about.”

Hart Hollywood is available on ASOS now.

Spencer Hart’s made-to-measure and bespoke tailoring services are available at 62-64 Brook Street, London, W1K 5DX.