One night in 1982, a 19-year-old club kid called Ian Griffiths, who had recently dropped out of an architecture degree because “there was just too much fun to be had in Manchester, to be honest”, was at a party in Wythenshawe. He was living on £37.50 a week benefit, and “perfectly happy. I made all my own clothes, I got into all the clubs free.” When the Haçienda nightclub opened in the city, Griffiths went every night without fail for the first six months – “and I didn’t eat anyway, so there was no requirement for food. But there we were, wasted on the sofa, and the news came on that Margaret Thatcher was considering conscription for the Falklands war for the unemployed. So I thought I’d better do something. That’s how I ended up studying fashion.”

The brand Max Mara conjures an image of camel coats and conservative northern Italian style, so Ian Griffiths, its designer for three decades, is not what you might expect. The man sitting opposite me in the Guardian canteen – the unstarry interview location was his choice, being close to where he lives when he is in London – is the most influential British designer you have never heard of. With annual sales reported to be more than £1bn, Max Mara is that rare thing, a fashion-week label whose heart is in the real world. For six decades, Max Mara did not have a public-facing designer – a unique move in the gladiatoral arena that is Milan fashion week, where Donatella Versace, Giorgio Armani and Dolce & Gabbana are all represented by personalities as well as brands. And then in February last year Griffiths cast Halima Aden in his catwalk show, making Max Mara’s the first Milan show to feature a headscarf-wearing model. Before the show, Griffiths told Luigi Maramotti, the chairman and owner, about the casting. “He said it was fine, but that he hoped it wouldn’t attract too much attention. Of course it did attract attention. But Mr Maramotti was delighted because that reaction was entirely positive.”

The Max Mara resort show, June 2018. Photograph: Max Mara

But at heart, says Griffiths, “Max Mara has always been radical.” He is turned out like an Italian tailor’s fantasy of an Englishman, in a navy double-breasted suit by the tailor Timothy Everest, who has made all his suits to measure for more than two decades. (“Once you get a taste for bespoke, anything else is like wearing a cardboard box.”) The folds of the silk pocket square in his breast pocket and the side parting in his light brown hair both appear to have been drawn with a ruler and compass. He is the most dapper punk you will ever meet, but punk he still is, in his own way. “Max Mara was a very radical new idea when it began in the 1950s. It was about dressing women in order that they could go and be successful in the world – so not a conservative philosophy at all, quite the opposite. There is a great deal said about feminism in fashion at the moment, but Max Mara has been doing this in an under-the-radar way for 40 years.” Griffiths is proud that Max Mara was the first label to take a working woman, rather than a lady of leisure, as its aspirational icon.

The secret radicalism of Max Mara was a theme of Monday’s catwalk show in the brand’s home town of Reggio Emilia – but this time the message was in the location, rather than the casting. The Collezione Maramotti museum houses the collection of contemporary art that Achille Maramotti began around the same time he founded Max Mara in 1951. “He bought Burri, Fontana, Manzoni, Novelli, Twombly [who moved to Italy in the 1950s]. This was the most avant-garde scene happening in Italy at that time, and he was completely in tune with this aesthetic, at the same time as launching Max Mara, which is so classic.” The welded sheet-metal of Alberto Burri’s Ferro gave Griffiths the starting point for stiff ruched lines that demarcate a dress; the china-clay wrinkles of Piero Manzoni’s Achrome translate into a soft pleated skirt, but the real point, says Griffiths, is “the subliminal messages I wanted to send by relating these wearable clothes to the avant-garde art around them – that classic doesn’t have to be conservative”.

The Max Mara resort show, June 2018. Photograph: Max Mara

Griffiths pulls out his phone to show me a portrait taken of him by the renowned music photographer Kevin Cummins around the time he began studying fashion. In it, he is wearing a wedding veil. “That was a time of incredible self-made culture in that city. Ian Brown lived three doors away from our flat; we’d see the name Stone Roses scrawled in the stairwell and I’d say to my flatmate, do you think they’re any good? Shall we go and see them? It was a moment when we were making everything up ourselves: our clothes, our music, our image.” As luck would have it, the legendary designer Ossie Clark had just begun teaching fashion when Griffiths arrived at Manchester Poly. “I learned an incredible amount. He got me to think about clothes in relation to the people who would wear them. Once he brought along a corset he was making for Jerry Hall.” He moved on to the Royal College of Art in London, and a part-time job at Browns on South Molton Street, where the celebrated Joan Burstein put him in the new Alaïa section, “because she thought women would trust a man’s opinion over a woman’s, on body conscious clothes”. It was Griffiths’ first encounter with designer fashion. “I was making all my own clothes out of lining material. I couldn’t believe people actually bought such expensive clothes.” All 60 students on his course submitted a project for Max Mara, “except I nearly didn’t, because I was living in a squat in Bloomsbury and, the night before hand-in, I was still working on it when my felt pen ran out at 2.30am. I thought, oh well, might as well give up and go to bed. And just then my flatmate Trish, who had been clubbing, came in from Taboo and lent me a pen.” Luigi Maramotti, the son of Achille, asked Griffiths to go to Italy for a meeting; he joined directly after his graduation. But then, many of Max Mara’s Reggio Emilia workers “have been there all their lives. I have worked with my right-hand person for 28 years and that is quite normal for our company.”

Halima Aden in the Max Mara show, Milan, February 2017. Photograph: Daniele Oberrauch/REX/Shutterstock

The secret to the eternal appeal of Italian fashion, says Griffiths, is that “it is primarily about making you look and feel beautiful. It’s not about being an experimental canvas for outrageous ideas. The best of Italian culture – in art, in food, as well as fashion – always attempts to present as something accessible.” Home is a first-floor apartment in a 15th-century building. “Our palazzo – listen to me! Our palazzo, in the middle of our street, ha, ha – is like something out of The Talented Mr Ripley. We are adjacent to the bishop’s palace, so I get an Easter card from the bishop.” When not working, Griffiths and his partner, Mark, divide their time between Islington and a cottage in Suffolk. “You wouldn’t recognise me if you saw me in the country. I’ll be up to my elbows in soil in the garden and Mark will say, ‘Can you please at least put your jumper on the right way round?’ But I am never not thinking about work. If I am walking the dogs, I will be listening to the show music, thinking about the collection.”

Now, Griffiths’ personal profile is growing fast. “I didn’t go into fashion to be famous, so I don’t need for it to be ‘Max Mara by Ian Griffiths’ – I’m not that egotistical.” Nonetheless, he smiles when he says that “when I’d been with the brand 25 years, there was a feeling that I could be trusted. I felt that if the brand had a voice it could connect better with women. The collections we have shown since I was given a voice have been more emphatic. I can talk about things more clearly, now.” About making the catwalk a platform for diversity, he says, “I prefer the world ‘normalcy’. Because that’s what it is. If you walk down Bond Street it is completely normal to see a woman in a headscarf wearing a Max Mara coat, so it should be normal on the catwalk as well.”