With his imposing height, his healthy tan and his effortless cool - not to mention a flow of easy banter which runs from rugby injuries to bicycles via Alexander McQueen and soccer casuals - it's hard not to feel lashings of guy love for Patrick Grant.

Even his beard rocks. As he sips an espresso in the basement bar of a stylish Glasgow hotel, I wonder idly if there's a magic setting on his trimmer which is denied the rest of us mere mortals, a sort of tonsorial equivalent of Harry Potter's Platform Nine And Three-Quarters.

It's the only way to explain the magnificent, Clooney-esque "grizzle" that covers his cheeks and chin. Clipped and trimmed - but not too clipped or too trimmed - it's the sort of beard Action Man would have if he came to life, climbed into a three-piece suit, poplin white shirt and sleek black shoes and pitched up at the Scottish Style Awards with Barbie on his arm. Actually Grant will be doing just that next month: he's been nominated in two categories, one of them Most Stylish Male. Barbie will stay at home, though he may bring longtime partner Katie Hillier, the fashion accessories designer with whom he shares a house in London's East End.

Of course Grant's blokey twinkle will be familiar to fans of the Great British Sewing Bee, the BBC Two reality show which is to petit point what the Great British Bake Off is to choux pastry. But don't think there isn't steel behind his winning manner. Still only 41, the Edinburgh-born engineer-turned-fashion entrepreneur is also the owner of a Savile Row tailoring house, Norton & Sons, and a high-end ready-to-wear label, E Tautz & Sons, and for his efforts in that second endeavour he was named Menswear Designer of the Year at the British Fashion Awards in 2010.

This autumn he has cemented his growing reputation as the fashion world's tailor-of-choice by teaming up with Debenhams to create a more affordable line of classic menswear under the label Hammond & Co, where suits can be had for south of £300. If you think the name sounds made-up, think again: established in 1776, it once had a royal clientele and is another of the dormant companies Grant inherited when he bought Norton & Sons in 2005.

Debenhams first approached Grant shortly after his British Fashion Awards win and initially asked if he would design a range of suits for them. He was intrigued by the offer, but the more he considered it, the more he realised there was a gap in the market waiting to be filled with something more than just suits.

"Nobody was doing nice-looking clothes with an attention to cut and fabric at a less expensive price point, and it's actually not that difficult to do," he says. "So I went back to Debenhams and said: 'I think we're missing a trick here - I think there's a bigger offer we can make which includes beautiful overcoats, heavy-gauge knitwear, a few sports jackets and things in cloths that you generally don't see.'"

But while it's easy to understand what Debenhams gets from Grant - his expertise and Savile Row cachet, his name and his increasing media profile - it's harder to see what he gets from an association with a high-street retailer that nobody would describe as cutting edge.

Ah, he says, but that's the point. E Tautz now sells in nine countries but it has always been a source of frustration to him that many of the people who love the label's aesthetic simply cannot afford the clothes. An E Tautz suit costs a quarter of the price of a handmade Norton & Sons equivalent, but the price-tag is still likely to be around the four-figure mark. Besides, with brogues, tweed and knitwear - what you might call "the George Orwell look" - being the current look of choice for many style-conscious men, the high street is missing a trick by leaving it to established retailers such as Crombie and Jaeger to provide for them.

"For me this was an opportunity to take what I feel is a nice mode of dressing, and take all the clothes that I enjoy wearing personally and enjoy designing and thinking about, and make them much more affordable and with a much broader distribution," says Grant. "A big part of the enjoyment of doing this is seeing the clothes being worn."

As if to prove the point, he leans back and gives the lapel of his Hammond & Co suit an appreciative, never-mind-the-width-feel-the-quality sort of rub. "This is a great-looking suit, I think. For the money it's extraordinary. It's every bit as good as a Ralph Lauren suit that would set you back £1000."

Still, says Grant, it was never his intention for him or his clothes to have a mainstream profile when he took on Norton & Sons. Armed with a passion for clothes and a mixture of what he calls "naivety and enthusiasm" he took a step into the unknown when he brokered a deal to buy the ailing Savile Row business. It helped, however, that as well as an engineering degree from Leeds University and experience in marketing, he had an MBA from Oxford University's Saïd Business School.

"When I took over, the plan was to resurrect this slightly knackered bespoke house and see if we could get it back to rude health and take it from there," he says. "It was very plain to me when I walked into Norton & Sons that this was a business that had bucketloads more to offer. It just looked so tired. It was like some scrawny old donkey on the beach that you felt sorry for - but you knew that if you fed it and patted it and brushed its tail, it would come back to life and give great pleasure to lots of people."

It's a neat metaphor and one I can't resist picking up. You could just have shot the donkey, I tell him.

"It was at the point where the glue-maker's truck was just coming round the corner," he admits. "But I think a lot of people could have achieved what I achieved. It's not that I've done anything particularly difficult with it: we've put a lot of hard work into it, treated it with respect, spoken passionately about what it does to an audience of people that were very ready to listen. And, frankly, we got very lucky."

That luck came in two forms. First, in the person of Kim Jones, now style director at Louis Vuitton but an up-and-coming young fashion designer when he approached Grant through a mutual friend and asked him to help with the tailoring for his own collections. On the back of that association, other young designers such as Henry Holland and Motherwell-born Christopher Kane sought out Grant's services too. "And because McQueen was great friends with Kim, he became our customer and bought a lot of clothes from us. Suddenly we were the tailors that made for Alexander McQueen. All of a sudden we had something."

Then there was television. The same confection of looks, style, soft Edinburgh brogue and charisma makes Grant a natural for the small screen. He first popped up as a talking head in 2009 on BBC Four documentaries about Savile Row and the Harris Tweed industry, then again in Alastair Sooke's four-part history of the suit, broadcast earlier this year.

But it was Great British Sewing Bee which brought him to a prime-time audience. Featuring alongside Claudia Winkleman and May Martin of the Women's Institute, Grant acted as judge in a competition which sought to find the country's best amateur sewer. More than three million people tuned in for the final and an extended second series will broadcast early next year. "The positive knock-on benefit to the broader sewing and tailoring industry has been remarkable," he says. "We've all been slightly shocked by the level of interest in sewing."

So how does he account for it? "It's partly recession driven, but also a reaction to decades of anti-nostalgia. I think it goes back to farming and food production and all these things we're beginning to cherish again. We've just captured a little part of it."

If it seems a strange decision for Patrick Grant to change horses mid-career, to move from engineering into fashion, then it shouldn't. His Musselburgh-born father did something similar. He first harboured dreams of becoming a jockey - his step-father ran a racing stable - and then, perhaps as a result of being crowned the East of Scotland Jive Champion, moved into the entertainment industry. He would go on to manage the Scottish pop group Marmalade (this is after they stopped being Dean Ford And The Gaylords but before they had any hits) and by the time Grant was born in the Morningside district of Edinburgh in 1972, he had switched to the rather more serene profession of accountancy. He now runs a market garden in the Borders, living - at least as far as his son can discern - by a sort of barter system.

Grant's mother, meanwhile, worked at Edinburgh University, and the couple had enough money to send their son to first the Edinburgh Academy and later Barnard Castle School in County Durham. Old Boys include fashion designer Giles Deacon, who was a few years above Grant.

"My parents thought it would be better for me to be away from home," Grant explains when I ask why he left Edinburgh. "They have good friends who live not far from Barnard Castle and their two sons were there. So they knew the school and said it was good for rugby and I was mad on rugby."

That obsession also saw Grant play No.8 for his various college teams after he left school and, despite a bad shoulder injury, for Edinburgh side Watsonians. When he was 30, he finally woke up to a fact most rugby playing schoolchildren learn much earlier in life - "It's a hard, physical game" - and hung up his jockstrap for good. Not the Lycra, though: he still cycles and recently completed the Scotland Coast To Coast Adventure Race, a 105-mile trek which also involves running and kayaking.

I can't say how good he looks in Lycra and, frankly, I wouldn't take my guy love quite that far. But he himself admits that suits have always, well, suited him. "I look better in tailoring than I do in other stuff so I've always gravitated towards that," he says. A particular favourite from days (and nights) gone by is a "sand-coloured, mercerised cotton Dries Van Noten summer suit" he used to wear to go clubbing in the early 1990s. Another early purchase was a Paul Smith suit that he "wore to death".

This, of course, was the era of Britpop, though by then Grant had been through his scruffy phase, first as a raver ("bell-bottom jeans and floral hoodies," he confesses) and later, after a spell travelling and working in the United States, in a hip-hop-inspired get-up of Air Jordan trainers, "big" jeans (whatever they are) and "authentic, triple-knit Champion hoodies". He reels off the label names with relish.

So, a soccer casual in all but name then? "Yeah, probably," he laughs. "I remember being given a pair of [Sergio] Tacchini tracksuit bottoms by a Hibs casual friend of my sister's who'd nicked them. He was 5ft 6in and I was 6ft 2in so he said: 'Here, you have these.'"

It wasn't Grant's only brush with the clothes-obsessed fans who followed Hibernian FC and other clubs in the late 1980s and early 1990s. In a summer job selling ice-creams in Princes Street Gardens the then-public schoolboy worked alongside another member of that unloved style tribe, also a Hibs fan.

"That was where I got introduced to labels like Chevignon and Chipie and Stone Island," he says. "We'd be in the booth opposite the bandstand and a couple of Italian tourists would come through in Stone Island jackets and he'd nip off and get on the pay phone and ring his mates.

"They'd follow these tourists, hold them up and steal their clothes, which they called 'taxing the tourists'. But back then there was nowhere in Edinburgh you could buy these labels."

That's not true today, of course, when virtually anything is available at the click of a mouse (though you still have to pay). But it demonstrated to the young Patrick Grant a fact that still holds true: where clothes are concerned, people will always crave the latest or the best. While he's happy to flirt with the first, Grant has made his area of expertise the second, hitching his love of clothes to Savile Row's centuries-old reputation for excellence in tailoring. To date, they have made a formidable team. n

The Hammond & Co range is available in Debenhams' Glasgow and Edinburgh stores and at debenhams.com. The Scottish Style Awards take place on November 9 at Kelvingrove Art Gallery and Museum in Glasgow. Patrick Grant is nominated in two categories, Most Stylish Male and Menswear Designer Of The Year.