HE BEGAN WITH A BOX OF LEGO. NOW HE'S GOT GRAND DESIGNS FOR THE CITIES OF THE FUTURE. AND FOR RADICAL ARCHITECT PAUL STALLAN , UPSETTING PEOPLE IS JUST PART OF THE JOB

As he speaks, he points out new developments along the river: Pacific Quay, where the BBC Scotland and rival broadcasters Scottish TV will eventually decamp to; the site of the Riverside Museum, where work is scheduled to begin in 2007; and Glasgow Harbour, a 130-acre brownfield site that will one day house 6,000 people. It's as if, Stallan says, the city is on the march down the river. "I think the edges of Glasgow are now blurred."

Stallan himself has been involved in both the Pacific Quay and Glasgow Harbour projects, but his principal contribution to this riparian renaissance is upriver a meander or two and will, he hopes, bring Glasgow's city centre back into focus. The architect is working on the ambitious, costly (to the tune of pounds-200m) and by no means uncontroversial Custom House Quay project, which includes a 24-storey narrow tower and which got the go-ahead from city councillors just over a week ago.

"The idea, very simply, is to bring Buchanan Street down on to the river, " Stallan explains.

"Buchanan Street was voted the second most popular shopping street in the UK, but literally 100 yards away you get junkies, prostitutes and dereliction."

Until recently, Glasgow was rather slow to see the potential of the natural resource that cuts it in two. Anyone who decides to take a walk along the Clyde from, say, the Exhibition Centre to the city centre is, if not "taking their life in their hands" as Stallan half-seriously suggests, at least exposed to a rather grim vision of the city's "ripped backside", as Iggy Pop might put it. Yet over the last decade the Thames, the Tyne, the Lagan, the Mersey and even the Irwell in Salford have become central to cultural and economic regeneration in the cities through which they flow. Now Glasgow is catching up, with a pounds-4bn plan to revitalise the river, championed by former council leader Charlie Gordon . . . and Custom House Quay is at the heart of it.

"It's a sort of once-in-a-lifetime offer, " Stallan says, "because the developer behind it is funding it singularly. It's not an institutional development; it's not Standard Life." The developer in question is an Australian, Rodney Price, who has already helped transform waterfronts in Sydney and Melbourne. "He has an interest in Glasgow, " Stallan explains. "He likes the city and he's genuinely interested in creating a vibrant piece of waterfront. He's said categorically to Charlie Gordon and others he could take his money, put it in Dubai and make six times what he's making in Glasgow."

Rodney Price is not the only one who likes Glasgow. Although he describes the relationship with the city as more "love-hate" than just "love", Stallan admits he can't imagine living and working anywhere else. "I go cold turkey going to Greenock, never mind Dubai." I'm not entirely convinced he's joking.

Nosingle architect could be said to be responsible for shaping a city the size of Glasgow, but it's fair to say Stallan is giving it a square go. Around the corner from Custom House Quay (and at the opposite end of the spectrum), he is working on a "micro-project" with the artist Peter Howson. This is a studio cum cafe/retail opportunity for the charity First Step, which will allow Howson to take on three or four students a year. The site is an old Glasgow steamie, which Stallan reckons is "just so Peter". Then there are his plans for a new campus and faculty building for North Glasgow College . . . a homecoming of a sort for the Springburn boy. "What we are doing is very, very radical. The building is effectively a gigantic monolith, a sort of iceberg in form.

Effectively the brief is to make a building that will be exciting and sculptural and in some ways provocative, to really put Springburn on the map."

Looking at the model, provocative is indeed the word. And the more time you spend with Stallan, the more you realise it applies to him too. At 37, he has been flying under the radar for years. While his employers have been making headlines (and not always good ones) for their work on the Scottish Parliament, Stallan has been building up RMJM's Glasgow office (he's currently in charge of 35 staff ) and building a portfolio that saw him named Architect of the Year at the Scottish Design Awards in May. He says he is "kind of embarrassed" by the award, but it does seem to have spurred him to start talking. Soft-spoken as he is, dig deep enough and you'll find flinty opinions about bodies such as Historic Scotland and the Glasgow Housing Association, and even about individual councillors. Today they don't need much excavating.

Yet being provocative, in word or deed, is not a quality everyone relishes in an architect, or indeed an architectural project. When the Custom House Quay project was first mooted, organisations including Historic Scotland, the Royal Fine Art Commission for Scotland, the Architectural Heritage Society of Scotland and the Glasgow Institute of Architects voiced objections. In a letter to the council, Historic Scotland accepted the scheme had "considerable architectural merits" but argued that "this cannot and should not influence the fact that the location is entirely wrong and that the development will damage Glasgow's historic architectural and cityscape character".

In particular it was worried about the impact on six listed buildings that would be affected by the development, including the Custom House itself. "I think they would rather see the quayside as a heritage theme park, " Stallan says. "In the quay project we are building into the river, and we've got people like Historic Scotland and others saying, You can't possibly do that.' But you only have to look at what people did at the turn of the 20th century. It's just unbelievable."

For its part, Historic Scotland says it is very supportive of regeneration and the use of the historic environment as long as the development is appropriate. It has worked successfully with Stallan in the past, a spokesman points out, adding: "We are often accused of saying no to a development. Historic Scotland has no authority to say no." The Custom House Quay project next goes to the Scottish Executive.

Still, Stallan believes the dynamism of the Victorians has been replaced by an obsession with Victoriana. "Historic Scotland and other very conservative conservation groups have expressed the view that this is a Victorian city and this is precious, " he says. "I'm firmly a Glaswegian, I fully believe in the city. I want it to be metropolitan, cosmopolitan, interesting, successful. I want tourists to come. I want it to be vibrant. I want employment."

Stallan is utopian about the potential of architecture. "We definitely have a role to create better communities and places, " he says.

Architects, though, don't always have the final say. However they may like to reinvent a city, it's just ink on paper (or pixels on a computer screen) unless the political will is equally ready to embrace change. So how does Glasgow's body politic measure up? Well, Stallan says, some of them are trying their best. "The planning authority are doing a fantastic job, " he says. "They're stretched to their absolute limits.

I really feel sorry for my planning colleagues, because it's an unenviable task."

He's not so kind to other departments. At the end of June the Glasgow Housing Association (GHA) announced a five-year, pounds-630m plan to transform thousands of homes . . .

the biggest investment in Scottish housing for decades, following the transfer of more than 80,000 council homes to the GHA two years ago. "This is great news for tenants in our local communities, " said Sandra Forsythe, GHA tenant chairwoman. Stallan's description is rather different: "unforgivable" and "frightening" are the words he uses. The reason? GHA, he says, has failed to embrace the concept of urban design. "You only have to look at their website to realise that it's lowest-commondenominator stuff. The politicians think it's reasonable to provide wee Jeanie with a roof over her head, double glazing and a new kitchen. But it's so unambitious."

Later, he sends me an e-mail that goes even further. "We need to provide homes', not houses' . . . we need people to love their environment. To love a place it needs to have character, style, individuality, tendered landscapes . . . art, play-parks. In short, we need to provide architecture and urban design. I have read just about every document that the GHA has published and there is absolutely no mention anywhere of architecture or design.

The bulk procurement' statements written in these documents might have been issued by a former Soviet Union housing department."

Unsurprisingly, the GHA doesn't agree. Its head of regeneration, Danny Bradley, says design is very much part of the plan. "We are well aware of the importance of good design. We fully agree with Mr Stallan's view that communities should have character, style, individuality, landscaping, art and play areas, and are working with four consultancy teams, incorporating architects, planners and urban and landscape designers. We have also produced a GHA design guide following consultation with professionals." A pounds-6m investment in improving the quality of neighbourhoods has already been announced, Bradley adds.

Stallan has had political run-ins before. In the wake of one of RMJM's first jobs in Glasgow . . . the revamping of the Tron Theatre . . . a city councillor, now an MSP, vowed the architect would never work in the city again. "Pretty scary for a guy starting out, " he says.

He fears there is a deep vein of philistinism running through political circles in Glasgow . . .

and in Scotland in general. Many politicians believe design automatically costs money, but it's not necessarily so. At one point he shows me a computer projection of his plan for a new football stadium for Hearts . . . "a bit of a flyer", he admits. The accepted cost of a stadium runs to about pounds-1,000 a seat. By excavating a site rather than building on it . . . ie digging a hole, laying the pitch at the bottom of it and using the earth removed for the stands . . . Stallan thinks he can do it for pounds-500 a seat. Similarly, good design, he suggests, could improve social housing at a less-than-premium cost. But it's an idea that's just not being taken onboard by politicians. It's a cultural problem, he says: "There's that beancounter mentality, which is a peasants' view of life. It just doesn't have to be this way.

"People can maybe criticise me: You're just a pie-in-the-sky architect.' But that's not the way I see it. I believe I'm feet-on-the-ground. My granny lives in Possil. I want a better home for her, a better environment, a better community."

Stallan's own story is a Glasgow tale; a personal microcosm of the city's modern history. He was born in Springburn, in the north of the city, to a family singularly lacking in silver spoons. "My mother and father didn't have anything, and we grew up in a single end:

a toilet and a stair. It's funny. I talk to the older generation and they say, You can't have, you look too young, ' but this was not that long ago."

The family moved to Maryhill and Kelvindale, then out to the estates . . . Drumchapel and Easterhouse. The young Stallan saw the fabric of working-class Glaswegian life break down on the journey; "the breaking down of that whole sense of place. And I think that sense of place has come full circle, because people now recognise it's not just a numbers game. It's not about providing homes: it's about creating a community, a space, a landscape . . . though there's a danger that the GHA will forget those lessons."

Ask him when his interest in architecture started and he says: "It was probably a box of Lego. That and living in a very, very, very small house. I guess I just dreamed of having existential amounts of space, you know?"

Maybe the fact his father, Douglas, was a draughtsman had some bearing on it too.

Certainly, he says, he was always drawing. "I was very visual, so architecture suited me."

Not that his progression was totally serene.

His teenage years sound like something of a switchback ride. He says he wasn't academic, and there was a period where he spent his days drinking wine in the park, smashing windows "and generally being a bit of a tearaway". Yet he won a place at university when he was just 16, and couldn't wait to get there.

Actually, he says, he was "desperate" to leave school, desperate to get on . . . almost neurotically so. "I guess I grew up very quickly. And I sensed that in some way I wanted to look after my mother and father."

His mother, Janette, had always pushed him hard. "She always wanted the best for her children, " he says. "Growing up when your parents don't have very much, they invest a lot in you. In some ways it's an enormous pressure." Certainly, he paints a picture of a rather earnest nascent adult. "I would have liked to have been more relaxed as a young man, more comfortable within myself. A great part of my restlessness and energy was having that feeling not to fail."

Presumably that's what drove him to work 12 and 14-hour days, year after year, as he kickstarted his career. "It's almost a drug, because I got so involved in projects and enjoyed it so much." Long hours are something of an occupational hazard, he says. Engineers work half the time architects do and are paid more, he says, "for the simple reason that architects give more away for free because they love what they do. Engineers can command better fees because they're more detached or dispassionate."

After graduating from Strathclyde university in his early twenties, Stallan lucked into a good first job working in Glasgow's peripheral estates under Peter McGurn, "a godfather for community architecture". On his first day he was charged with taking children from a housing co-operative in Easterhouse to the swimming baths. "You have these grand aspirations, thinking you'll change the world, and I'm buying crisps and Coke.

Working with McGurn gave Stallan a chance to see the scope of an architect's work. "He was so well connected, and we had interesting clients: Robbie Coltrane, Bill Forsyth. In the mornings you were doing housing projects for these people, and in the afternoons you were out doing social surveys. It was a great experience."

Certainly, it is an experience that seemed to ground Stallan. On leaving university he had, like many of his contemporaries, dreams of conquering the world: "I had visions of going to Los Angeles or Boston or London and working with prominent architects. Most of the people I studied with have left and are working overseas. I'm probably one of the few who stayed and got stuck in, and I don't regret it. The opportunities were harder to come by working in a culture that isn't design-alert, if you like, but it brings you down to earth."

After working for McGurn, Stallan did a little international work before helping establish RMJM's Glasgow office. He also got married . . . to Seonaid, a teacher . . . and the couple now have two children, Dylan, seven, and Rowan, five. But he was still working too many hours: building a business, building a life, even building a house. "I was knocking the doors down. It was a bombsite. We were living in a building site with two young kids and the business had just secured the parliament project. It was just absolute mayhem."

That mayhem caught up with Stallan some seven years ago when one day he simply collapsed from exhaustion. To add to the cocktail of stress and overwork, he was then diagnosed with clinical depression. Did he not see it coming? "In that state of mind you don't really know you're dysfunctional until the wheels fall off, " he says. Fortunately, he was able to re-attach them. He started to delegate work, took more time off, and "recognised that it's not all about me".

You could argue that this philosophy now defines his architectural approach. It's a collaborative effort, and he's keen to involve others in the design process. He speaks approvingly of his involvement with the Glasgow artists Richard Wright and Andy Miller, citing the example of Miller's involvement in RMJM's masterplan for a city in Dubai. "We brought him in because we were inventing this skyline from nothing in a piece of desert, " says Stallan.

"Andy came in and treated it like a painting.

Visually we weren't pushing it far enough. He was flipping blocks, folding blocks, knocking blocks down, generally creating a rhythm and composition. Andy spends all his time placing objects and thinking about colour and light and space. Sometimes you need that input."

Despite his beefs with Historic Scotland and the GHA, he thinks his input, and that of his contemporaries, is becoming more accepted.

The public, he says, seem more interested in architecture and design. "Definitely. I blame Carol Smillie. Our clients are increasingly embracing design and have confidence now.

I've definitely seen a shift in the last five years.

I've seen my own parents go from quite a conservative interior within their home to being quite radical."

In the bigger picture, though, quite radical is not radical enough for Stallan. He wants Glasgow . . . and Scotland . . . to embrace the idea of design; to export it, even. We're all familiar with the concept of boutique hotels; why not a boutique country? "As a small country, to stay ahead of China and India we have to differentiate ourselves as a think-tank for the world, " he says.

That's the dream: a kind of Herbert Ypmaapproved designer nation. Beautiful buildings for a beautiful country. Scotland the braw. Too often, though, Stallan argues, we're stuck with the nightmare. "It's that old-school pennypinching conservative mentality, " he says. "You only have to look at the Private Finance Initiative for schools. Highland schools, for example, were reviewed recently and the schemes are so bad that Architecture and Design Scotland [the national design body] begged the council not to take them forward, but they had no choice.

They had only one bidder, and it was basically take it or leave it. And as long as it keeps the rain off the kids, it's good enough. But when you're working in these amazing environments and you're putting up the most dreadful architecture and design, that's just not acceptable."

What was it Oscar Wilde said? "We are all in the gutter, but some of us are looking at the stars." Paul Stallan wishes a few more of us were willing to get our telescopes out.