Head to the Paul Smith store on Albemarle Street on a Saturday afternoon and you will find a certain septuagenarian thumbing the fabric swatches found there. He isn’t here to shop. Recently reinstated as the creative director of his eponymous, almost-50-year-old label, Sir Paul Smith is a busy man. Not too busy, mind, to miss his Saturday shift in his flagship boutique. It’s a work ethic that has defined a career; a determination that has taken a fledgling shirt business from a tiny, windowless room in a Nottingham back alley to the four corners of the globe, with products ranging from shoes to wash bags to cycling helmets – and everything in between. Smith’s fans include the head of the Bank of England, Paul Weller and Tom Cruise. In Japan – where he has become something of a Britpop icon – he gets stopped in the street for selfies. Despite the success – some 300 stores worldwide, 20 in the UK – Smith remains level-headed when considering his achievements.

“I grew my business very gradually, so there was never a break-through moment when it went off like a rocket,” he says. “I’ve held my nerve, and that’s why we’ve had such steady growth over the past five decades. I stick to what I know and what I’m good at.” What he’s good at, very good at, is classic suiting with contemporary, kooky twists; jaunty socks in hypnotic hues; shirts, shoes and leather accessories in signature rainbow stripes. The designs are as playful as the man himself. In Smith’s Covent Garden office, there is an inspiration room of curious objects dubbed the Stockroom of Silly Things. Sir Paul has been known to produce a comedy rubber duck during gloomy boardroom meetings. After temporarily passing the creative director reins to his then head of design Simon Homes in 2015, Smith is back in the creative driving seat. Here he discusses his plans for the future, his top British designers and his enduring love affair with London.

Growing up as a kid in Nottingham, music was initially the reason I’d visit London – for gigs. I remember crashing on the floor of a mate’s house when the Notting Hill Carnival first started in 1966. At that time London was so full of creative energy – musically, fashionably and artistically. I’d come down for a few days and we’d just go out to different gigs every night. Sometimes I’d print a few T-shirts back home in Nottingham and bring them with me to sell to people in the audience. Any money I’d make would go towards paying for the petrol to get me there in the first place.

I love the creative confidence that Londoners have. The idea of clashing different styles is really central to Paul Smith; taking something classic and familiar and twisting it with the unconventional. For example, pairing a suit with a white T-shirt and tennis shoes. At the risk of sounding swell-headed, I really did pioneer that softer, more casual approach to formal tailoring.

London has always been an exceptionally creative and cosmopolitan place. With the British Museum, the National Gallery and Tate Modern, we have three of the most popular museums in the whole world. There’s just an endless flow of inspiration. There are more than 300 languages spoken here, more than anywhere else in the world. It is a fantastic goldmine of ideas.

I don’t find that inspiration really works in a very A-to-B way. When people ask how I find inspiration, I always say ‘inspiration is everywhere; if you can’t see it, look again.’ Sometimes you just have to look up from your phones when you’re walking down the street and you’ll notice a clash of textures on the façade of a building, or a particular combination of colours.

I wear a suit more or less every day. It’s like a uniform. I feel my most comfortable and confident in a suit. Day-to-day, I wear a classic navy two-piece, but on a particularly special occasion I might wear something bolder – a dark green wool with a white check, for example. I have a pair of handmade leather shoes from Paul Smith that I’ve owned for 35 years. In today’s world of fast fashion they’d be considered fossils, but I find they just get better with age. They’re a simple Derby in brown leather, handmade in Tuscany. I don’t get too attached to clothing, but I would hate to lose these.

I don’t spend a great deal of time thinking about the future. There’s so much noise going on in the world today, the main thing is to stay focused on today and tomorrow and maintain a clear point of view. There’s a lot of change taking place in the industry now but I try not to get too preoccupied with what’s going on around me. The speed with which everything is happening can sometimes be a little scary.

It’s great to still be so involved with the brand. In the fashion industry, so often designers disappear into an ivory tower and lose touch with the customers they’re designing clothes for. I always try to maintain awareness. There is such an amazing pool of creative people in Britain. John Booth is a young London-based ceramic artist whose work is great; it’s colourful and playful, two things that Paul Smith is famous for. We sell his pots in our Westbourne Grove and Albemarle Street stores.

Holland Park is where I’ve called home for many years now. It often feels like a little village within London, which is very special. There are great parks right on the doorstep and we’re close to Portobello Road market, which is one of my favourite markets in the whole world. I also love the Lacy Gallery on Westbourne Grove. It’s stumbling distance from my shop and is a very special little place. If I’m looking to get something extra-special framed, I’ll always pay a visit to Lacy.