More flamboyant designers such as Jean Paul Gaultier and Yohji Yamamoto might disagree. Their work often suggests they feel stifled by the formality of menswear, but Van Assche revels in the discipline that he imposed on a faltering Dior Homme when he became creative director three years ago.

'Menswear is more about evolution than revolution,' he says. 'You can't get away with the slightest mistake. Half a centimetre the wrong way can destroy a shoulder. And I feel quite comfortable with that.'

Van Assche might be in his comfort zone now but it took him two tough years to get there. Although Dior has been a fashion house for more than 60 years, Dior Homme was created a mere 10 years ago, under the leadership of Hedi Slimane, a French designer known for his love of indie rock and friendships with Lady Gaga and Babyshambles' lead singer, Pete Doherty.

Belgian-born Van Assche became Slimane's assistant shortly after he graduated from the strict confines of the Antwerp Royal Academy of Fine Arts. He lived in his master's shadow for more than half a decade before launching an eponymous menswear line. Then Slimane left in the midst of a controversy - it all hinged on what he saw as a lack of independence - and Van Assche was handed the reins. Many people said he would not be able to survive the departure of his mentor, a man who made men's fashion sizzle on the runway with the kind of buzz normally associated with womenswear.

'The first two years were quite tough, mostly because people didn't really want me to succeed,' he says. '[Slimane] defined the first part of Dior, which was obviously very important because that got the name out there. But whether it was me, him or somebody else, somebody had to take it to the next level.'

Slimane had created what Van Assche calls a 'niche brand' and the Belgian's first task was to move beyond that.

'Dior Homme could not stay a niche brand in a big house, somebody had to take it somewhere else,' he says, with an air of calm authority. 'I enjoy the fact that more men now seem to feel the appeal of the brand. It can be the 16-year-old Japanese fashion kid or it can be a 60-year-old politician. I feel very comfort- able with that.'

The economic crisis hit in the middle of Van Assche's first two years on Avenue Montaigne, where Dior has had its headquarters, behind an ascetic facade, since 1946. The 2008 recession was an opportunity for Van Assche to question the direction taken by Slimane and he used it to change the orientation of the brand's clothes. But it took a personal revelation for him to find his way. Or rather to discover what his mentor - and by extension himself - had been doing wrong.

'I found the new voice for Dior in what was actually quite a silly moment,' he says with disarming charm. 'I offered a new Dior jacket to a close friend and I never saw him wear it. So I asked him why and he said, 'Well, I can't move in it.' And I thought, wow! It's true. It was a revelation. I saw that after the crisis people wanted no-nonsense fashion.'

The ultra-slim - some would say boyish - silhouette created by Slimane was a revolution in its time; it was launched in 2002 and it replaced the bulkier suits of a previous generation.

To look good in a Slimane suit men had to be ultra-thin - Karl Lagerfeld allegedly went on a strict diet to fit into one - and wearing them was all about striking a pose. A T-shirt by British designer Henry Holland summed up the garment with its slogan, 'Cause me pain Hedi Slimane'.

'Before [the crisis] people didn't really mind if they couldn't move,' says Van Assche. 'They only wanted to look good. To be a fashion icon or whatever, I feel people are still prepared to pay a big price, they still want to look great but they also want to feel comfortable and that is a new proposition for Dior.'

Van Assche says he is focused on finding a clear balance between creativity and comfort. Menswear has been through a profound revolution. Ten years ago most businessmen wore a suit and tie to work and men's fashion houses such as Dior Homme and Zegna did not have jeans or trainers on their racks. Now Van Assche designs both, along with bags that are handbags by any other name, belts, ties and watches.

'That is the difference between fashion and art,' he says of his additional workload. 'I have to relate to reality. The reality is an opportunity because it allows me to constantly innovate and create new aspects of the collection.'

To achieve this end, Van Assche is a tough taskmaster who runs his atelier with iron discipline, as if the right and wrong ways of doing things can be separated with the precision of a tailor chalking out a seam on black cloth.

'I am very conscious of my work schedule. I never disappear for two weeks: and I hate it when people are late because I hate myself when I am late. I have 15 people sitting in the atelier and every minute they are not working is a minute lost. Many of these people have 30 years of experience so why wouldn't I put that to maximum use? I never enjoy last-minute drama and changes. I am not that kind of designer: if a season takes five or six months you should use every minute to get things right, especially in menswear because there is really no excuse for a bad shoulder.'

The Dior Homme collection for autumn-winter shows Van Assche's concept of evolutionary fashion at work. He presented a reworked version of the skinny black suit, which no longer fits like an agonising straitjacket, and large military coats of the type that usually weigh a tonne but, through the innovate use of new materials, are as light and fluid as a cashmere blanket.

'It is comfort clothing and we are doing that with everything now, making things lighter,' he says. 'It's a new way of looking at modern clothing. You used to have high fashion with strict tailoring and street clothes that were baggy. And I have been mixing up these elements at my own label because that is what I want to wear, and now we are doing that at Dior ... because you are never going to get a 16-year-old kid to wear a suit that makes him feel like he is dressed like his father.'

With design responsibilities for his line and the Dior Homme brand, it is reasonable to expect that Van Assche might have some wardrobe suggestions. And he does not disappoint.

'A good suit definitely, one that I can move in. A white shirt, a black T-shirt, some sneakers and some good boots: the white shirt can be casual or really chic, the black T-shirt can be quite chic but also extremely casual; the boots the same. With these elements you can go anywhere and look good.'

Of course, Van Assche is not talking about any old black suit or white shirt. If his hands have been anywhere near the garments, they will be tailored with world-class precision and, increasingly, they will have sartorial touches that suggest he is no longer living in the shadow of Hedi Slimane.