The tricky thing about being granted an interview with Mr Tom Ford is trying to come up with a new way to conduct it. He’s done it all: he’s answered almost every intimate question you could imagine asking; chatted nude with The Sunday Times’ Mr AA Gill, and for another feature posed in the buff with two models in the shower. Basically, Mr Ford has nothing to hide. What you see is what you get: an enormously successful and driven designer and businessman who’s also absurdly charming, handsome, amusing, self-deprecating and, of course, stylish. All in all, rather intimidating.

It turns out, thankfully, that he does have one or two weaknesses. He doesn’t sleep well. Although he is careful with his waist – usually eating just sushi for lunch – he does have a predilection for Colin the Caterpillar fruit gums. “My assistants think I don’t like people who eat,” he says, laughing. “It’s true I don’t like to see or smell food in the office. But I don’t like the staff to leave the office, either. I’ve never actually seen anyone here eat. Perhaps they eat under their desks when I’m in here doing interviews.”

He leads a healthy existence these days – no alcohol, few carbs, early nights – partly because he’s getting older (he’s in his early fifties) but mostly because he’s the father of a two and a half year old, Jack, and that takes a lot of energy. Being a father means he has relaxed about some aspects of his life – house not as tidy as it was, grooming regime no longer as elaborate – but you wouldn’t know. His office is immaculate; his hair perfect, his facial stubble ink-black (he has help with the latter, he admits, as he’s not yet ready to be a silver daddy).

One word that has always been associated with Mr Ford is “sex”. Has fatherhood had any impact on that? Short answer: yes.

“I feel less sexy now that I’m a father – and actually there’s a scientific reason for that,” he says. “I read that men who are the primary caregivers of children have lower testosterone levels. It drops, according to some reports, because nature wants the man to stay with the children and not let them wander off… Now I don’t know if my testosterone levels have dropped or not, I haven’t had them tested, but I feel less sexy, definitely. ”

That said, he still enjoys shocking an interviewer with disarming candour. “I suppose stopping drinking made me feel less sexy, too,” he adds, unprompted. “I think that being drunk all the time used to fuel, and I don’t mean my sex drive, but my… you know, I did a lot of things with [risqué fashion photographer] Terry Richardson, that I wouldn’t have otherwise done.” He’s referring to the aforementioned shower shoot.

At the time he was building and running the Gucci group – which owned Alexander McQueen, Stella McCartney, Bottega Veneta and numerous others – as well as designing multiple collections for Gucci and Yves Saint Laurent. It’s hard to believe he could have done all this with a sore head. “I was a highly functioning alcoholic,” he says, without batting an eyelid. “I think I did a lot of things creatively that I probably wouldn’t have done had I been sober. In the end, they kind of all worked to my advantage.”

He sobered up after leaving the Gucci group in 2004, however, coming back with Tom Ford cosmetics, fragrance and eyewear, writing and directing an award-winning movie, A Single Man, and unveiling his own menswear label. This, from the beginning, has been aimed at a jet-set customer who appreciates not only how his clothes look, but how they feel and fit. The tailoring is classic yet distinctive – wide pointed lapels, a fitted waist, a liberal use of monochrome checks and stripes – and the sportswear so tactile and covetable that when you travel you want to book it in a seat next to you rather than check it in.

Though it’s undoubtedly designed to have fun in, it’s also a wardrobe for grown-up men. Does Mr Ford think that as a man’s lifestyle evolves, his wardrobe needs to adapt too? Will he always wear his uniform of a black suit and white shirt, I ask? “I don’t think you have to change who you are,” he says. “If you’re… someone who likes jeans, a leather jacket and a white shirt, I think you can stay that person, but I think that person at 70 is going to wear different versions of that or wear it in a different way. You know, I even wore this kind of thing when I was really a little kid; I was born 50 years old…

“I used to plan what I was going to look like at 50 years old. Yeah, I was going to have some grey right here – which I have decided not to have for the moment – I was going to have more hair [he smiles], but other than that I am exactly what I thought I was going to be.”

One imagines Mr Ford spends a long time getting ready each morning. But while he wakes early at around 4.30am, it’s due to an inability to sleep rather than a need to preen.

“I get up and make myself a gigantic iced coffee,” he says. “I then answer emails and work until about 6am. Then I will head upstairs and have a second giant iced coffee and lay in the bathtub. I don’t like warm drinks of any kind. I lay in my bathtub with a bendable straw in my coffee and no lights and only one candle lit. I love that time in the morning when no one else is awake, and I’m alone, and then I can slowly come to life.”

He insists his grooming regime is often low-maintenance. “Today, because I was having an interview, it consisted of trimming my beard.” After that, he says, he gets dressed and wakes Jack up at 7.30am. “Richard [he has been with his husband, Mr Buckley, an editor, for 28 years] and I have breakfast with our son until about 9am and then I leave for the office.”

Evenings, too, are now equally low key. If Mr Ford has to socialise, he tries to be home in bed by midnight at the latest. If he isn’t going out, he’s apparently in bed watching TV by 10pm. “Talk about unsexy,” he says. I’m not sure many would agree.