Meet Mr John Pawson, the minimalist architect behind the institution, which this month reopens in its new home.

It’s not every day that you get to have a one-on-one conversation with a starchitect about the complex philosophy and multi-layered tenets of minimalism beneath a brutalist, hyperbolic paraboloid roof. But here’s Mr John Pawson – immaculate, handsome, urbane, gently intense, cashmere-clad and prone to archly observed asides, doing just that.

What is minimalism exactly? Mr Pawson likens explaining its concept to the aesthetically ignorant as akin to educating someone with no knowledge or interest in football to the machinations of the offside rule. “Dinner parties can be difficult,” he says, raising an eyebrow. “I try to limit my response to just architecture rather than going into religion and art. For me, it is about clarity and being able you see things without stuff getting in the way everywhere. Paring everything down to its absolute essence so you can’t really improve it. Of course, materials are important, as are proportion, light and scale. I am aware that there are lot of ironies in place. Architecture with any kind of details costs money… but minimalism costs even more. It is hard work and you have to keep on going and going so that in the end, all the details add up to something very calm.”

Mr Pawson has built homes in Greece, California and Japan, worked on the designs for Calvin Klein’s New York flagship, the Christopher Kane store on London’s Mount Street and even a monastery in the Czech Republic. As he casts a knowing and critical eye over the interior of his chef-d’oeuvre, London’s new Design Museum – an expanse of beautifully finished Danish-oak benching, apparently floating against an illuminated wall, a perfectly polished, terrazzo stairwell and a lone, raw and handsome concrete pillar, proudly varicosed with shuttering marks – he says: “To me, that’s a kind of comfort.”

Certainly, all the required elements of Mr Pawson’s signature style have come together in this grand statement of beauty and clarity at his largest project to date (and his first ever public commission). The £83m project sandwiched between High Street Kensington and Holland Park opens its doors to the public this month. The building is a cathedral to elegant understatement: the long, under-appreciated and mostly unloved 1960s Commonwealth Institute reconfigured by Mr Pawson and his team as a warm and welcoming, “wow factor” multiplex of exhibition spaces, common areas, cafes, educational facilities, an auditorium and a store is a marvel. Intended not just for art students and design junkies but also for mums with pushchairs, school kids and people just wanting to hang out and have coffee, the new Design Museum rebrands Mr Pawson as the people’s minimalist.

“Students and pushchairs… I love all that,” he says, slightly hurt that MR PORTER should think otherwise. “I often nip into places – museums and galleries – for a pee and end up getting distracted, so I liked the idea of opening the building up to the park, encouraging people to come in, exposing them to different ideas of what design is. Challenge the modern idea of design just being all about expensive stuff you can buy.”

The project started almost a decade ago when Sir Terence Conran proposed the idea of relocating the Design Museum, which he had co-founded at Shad Thames back in 1989, to a bigger and better building. “To turn it into a world-class attraction,” says Mr Pawson. The team looked at a few sites around London, considered a wing of Tate Modern, but eventually decided on the Grade II* listed edifice originally designed by Sir Robert Matthew of Robert Matthew Johnson Marshall and completed in 1962. Or, as Mr Pawson likes to call it: “the tent in the park”.

Having purchased the empty plot, a developer snapped up the now redundant flagpole space at the front and secured planning permission for a residential block, gifting the apparently troublesome Commonwealth Institute to Sir Terence’s people completely gratis.

As it turned out, only the distinctive gazebo-like roof of the modernist building was listed. English Heritage and the Twentieth Century Society agreed that pretty much everything else could go. Pawson’s builders tore down the walls and most of the Star Trek-ish interior “until we just had the four concrete buttresses holding up the roof. It was a very scary moment.” Windows were installed, spaces opened up, light flooded in. “People who have walked past here for years but never actually noticed it before, come in and say, ‘Wow, I never knew it was so… spectacular.’”

Mr Pawson’s career in architecture began on a somewhat smaller scale. Born in Halifax, West Yorkshire, his father owned a textiles factory while his mother played the organ in the local Methodist church. “People always think it was my time in Japan that had the biggest influence on my career, but I reckon it was the bleakness of the Yorkshire countryside, the Moors, the 19th-century industrial buildings and my mother playing the organ that had the most lasting effect.”

He was schooled at Eton, evolving a series of stylistic obsessions on his way to flunking A levels. “From the age of 13, I wanted to be James Bond. I carried a brief case and even sent off to the US for an El Paso gun holster, just like the one Bond had in the films.” The holster was mailed to his Eton schoolhouse, where it was intercepted by the headmaster. “I hope there isn’t a matching hand gun on its way, Pawson,” quipped the beak. Did he ever wear it? “Of course I did. It was very uncomfortable – and looked silly because I had nothing to put in it.”

These days, he is happy doing site visits in a simple, 16-ply cashmere crew neck (“Loro Piana – incredibly light, incredibly soft”). But when he was a teenager, Mr Pawson, who had seen The Beatles play live at Halifax in 1964, tried his best to emulate Sir Mick Jagger’s wardrobe (“No good – because I had hips and Mick didn’t”). He eventually settled on copying the clobber and cantilever tonsure of Mr Billy Fury. “I had this great rock ‘n’ roll look. Especially with my hair. I used to go this barber called Heaps of Halifax where they’d sell you a bottle of ‘bug juice’ for your quiff. It set hard and dry, but the comb lines would stay.” At school, his fellow Etonians would muss up his do and ridicule his (now all but imperceptible) Northern accent. “It was serious bullying, but I was so thick-skinned and Yorkshire accented that I didn’t care.”

Leaving school, he embarked on the hippy trail through Afghanistan and across Asia, trying out the ascetic, whitewashed, proto-minimalism of Zen Buddhism before ending up in Japan, where he secured a short internship with the avant-garde architect Mr Shiro Kuramata. Back in London, Mr Pawson studied at the Architectural Association dropping out after just two years, preferring to cycle around town on his beloved Carlton bicycle (he is still a keen cyclist) visiting galleries and museums.

His first commission as a designer was transforming the Elvaston Place flat for his then girlfriend, art dealer Ms Hester van Royen. When the plaster and paint had dried, the writer Mr Bruce Chatwin visited and felt profoundly moved by its design. “I was taken to a flat in an ornate but slightly down-at-heel Victorian terrace, and shown into a room in which, it seemed to me, the notes were almost perfect,” he wrote in an essay. “I found myself walking around it watching its planes and shadows in a state of trance.” Mr Chatwin, with his Napoleonic camp bed and Peruvian Indian chief headdress wall hanging, quickly became Mr Pawson’s first celebrity client.

The Kings Cross-based architect was officially ordained as a “starchitect” in the early 1990s when he worked for Mr Calvin Klein on the US fashion icon’s Madison Avenue store. “I was trying to get this thing made that was designed by me, but was also very much him,” he says. “He had incredible energy and resources.” Was Mr Calvin Klein as fussy, finicky and as details infatuated as Mr Pawson himself? “Oh, much worse. He’d say, ‘Come over at 8.00am and we can have breakfast and talk about the store.’ We’d have lunch and dinner and it would get to 8.00pm and I’d realise that we’d been talking window fittings. For 12 hours.”

Now, with the Design Museum recently signed off and officially approved by Sir Terence Conran (“I couldn’t have done a better job myself,” he told Mr Pawson), current projects are more personal: the completion of an east London house for his son – Mr Caius Pawson, founder of the Young Turks record label, whose roster includes The xx and FKA Twigs – and daily updates of his Instagram account, as well as a country house comprising a series of converted farm outbuildings in the Cotswolds. “The house has to be the defining project because I have invested so much in it,” he says. “I have to get everything right. It is driving my wife [Ms Catherine Pawson] crazy. Sometimes I wonder if she is not of the faith.”

He’s kidding, of course. But at 67 years of age, has rural life not softened Mr Pawson’s rigorous aesthetic, maybe have him obsessing over details a little less? Can he, for instance, see a day when he will be less demanding, perhaps relaxing his “zero tolerance” ruling on clutter and cushions? The arch starchitect thinks for a moment and then delivers an appropriately minimalist response: “No.”

**The Design Museum reopens in its new location on on 24 November **