It’s been two and a half decades since Matthew Williamson founded his eponymous fashion house and launched a dazzling career as an award-winning style trailblazer and regular face on the Noughties party circuit. His acclaimed, colour-block-filled debut collection, ‘Electric Angels’, showed at London Fashion Week in September 1997, and introduced the world to his technicoloured vision. Since then, his signature use of bold colours and vibrant patterns has guided him, in more recent years, from high fashion into the world of interiors.

When we speak, Williamson is at his home in Mallorca, and his soft Mancunian lilt doesn’t seem to have taken on any Balearic inflections. It’s a far cry from the streets of Primrose Hill, where he famously bought his first house, and would be photographed regularly with his muses and models Sienna Miller, Madonna and Kate Moss in his runway-ruling heyday.

Today, Williamson spends his time developing homeware collections to sit alongside his growing residential and commercial interior design portfolio. He’s just unveiled his latest project: the new Design Kitchen in the Sachs Family Park Room at the Design Museum in Kensington. Inspired by the views over Holland Park, and the juxtaposing architecture of the stark, minimalist structure of the building, the Design Kitchen entices visitors to meet, relax or work remotely with its cocooning green banquettes, soft lighting, and eclectic interior trimmings.

He was excited by the “open-ended” brief that came with this design job, as well as the hard graft, he explains. The area had to function as a public space, and he had to keep to a modest budget. “I was catering to an in-the-know audience, people who had made the journey to see good design,” he says. “The space was brutal, angular, and graphic, but powerful in its pared-back simplicity. It was my job to bring it to life.”

Williamson has used a rich palette of varying tones of green, pulled together with a sprinkling of mid-century furniture, hand-blown glass lighting, velvet, and printed upholstery. He also worked closely with UK-based artisans and brands to create a comfortable atmosphere. “I wanted to bring the outdoors in,” he says, laughing, conscious that he sounds cliché. The space is still ‘Matthew Williamson’, but only to a point. “It wasn’t me doing me to the ‘nth’ degree, I wouldn’t say. The brief did not call for maximalism. So, in many ways, I did have to reign it in. But I like to think that if you walked in and heard I’d done it, you’d say ‘yeah, that makes sense’.”

The green tones create a smooth light-to-dark gradient across the seating and woodwork, set off by smart, black marble-top bistro tables. Each alcove features a green Planet pendant ceiling light from his collection with John Lewis, as well as his cordless Phileas table lamps designed for Pooky. Hand-blown glass and vintage ceramic wall lights from Curiousa and marble and rattan table lamps from Lights&lamps complete the scheme.

“I love the ombre effect created by the wall of banquettes that run along the window,” he says, when questioned on his favourite aspect of the room. “It has a real American diner feel, lifted through elegant design. It’s a private little nook, perfect for a meeting or quiet lunch.” He also has a particular fondness for two big club chairs, which, ironically, are covered in a foliage fabric named Richmond Park. “I’ve had my eye on the fabric for ages and had been desperate to use it. Shame about the name though…” He also loved the opportunity to give so many pieces a second home. “From a 1970's battered brown leather couch to the repurposed rugs, we were able to bring an authentic, homely feel to the place with vintage finds,” he explains.

Williamson is no stranger to the Design Museum, and we discuss exhibitions past and present, from the current Rebel: 30 Years of Fashion installation that he’s desperate to catch (and features in) to his own dedicated show, Matthew Williamson: 10 Years in Fashion, back in 2007. Conversation drifts to his seemingly stark career turnaround, having left behind success in the world of high-stakes high fashion for that of soft furnishings. “I technically left the industry in 2016 because honestly, I had just become so jaded with it all,” he says. “And I knew I was more than capable of making the shift. I would describe it as a pivot, more than a departure – or jumping off a cliff, for that matter. It was a gentle progression into dressing rooms instead of people. At the end of the day, it was still the same blank page.”

Almost overnight, his enriching wallpapers and fabrics permeated the interior design world, a blanket, banish-the-beige stance against museum-like minimalism at home. From meadows to birds of paradise, starry skies to temples, you can spot his soul-lifting hand a mile off. With such an incredible career both behind and in front of him, Williamson is down-to-earth, friendly, and humble – exactly how I’d remembered him from an interview years ago at the launch of his first bridal collection.

I ask about some of his favourite fashion designers and he admits he doesn’t even follow what’s going on anymore. So, I take his lead and ‘pivot’ to his proudest career highlights –and his response is anything but ‘jaded’. “My first show in 1997 was a crucial moment. It launched my career at the age of 25. Opening my stores in Bruton Street and New York were also fundamental milestones. Releasing my self-titled book with Rizzoli was also great.” Hot off the press, his latest interior design book, Living Bright, is also an eye-catching gem of a tome.

What would his advice be to anyone thinking about a career shift like his? “I’d say put your phone down and grab a pen and paper. Start using your hands again.” He recalls a letter he wrote to Christian Lacroix, a huge inspiration of his when he first started out. “Getting a written reply made all the difference. It was the human, personal touch. Nowadays it would be so unusual to get sent anything by hand, especially something like a presentation of designs. It would really make you stand out.”

But for all the talk of departures, he casually drops in a desire to design kidswear, inspired by his seven-year-old daughter Skye. Williamson's main aim with his interiors, he says, is to be “warm, non-intimidating and uplifting” - which pretty aptly sums up the man himself. With so much still on the horizon, from going back to clothing to new high-street collaborations, all we can say is, watch this emerald-toned space.