Mary Portas has a high opinion of Belfast. Well, as high as might be hoped. " All my cousins live in Northern Ireland and I love Belfast. I think it has a real buzz, but sadly too many of the recognised names in the UK have gone there. I'd love to see more independent stores thriving but Belfast certainly has a great energy."

Glowing praise indeed from the 'retail marketing guru', famous for delivering harsh judgment on shops that don't meet her high standards of style or service. In her TV series last year, Mary, Queen of Shops (a new series is due to air shortly) she tried to turn around the fortunes of struggling shops, often taking radical action.

She is visiting Belfast to deliver masterclasses to the retail industry workers as part of FASHIONWEEK.

"I'll be imparting knowledge on what I think is happening in retail and what I think the future will be," she says. "Also, I will be giving tips on what I think will inspire people to think outside the box on what they're doing, how consumers are buying, understanding how shoppers are shopping - in order to make it fabulous."

'Fabulous' is something Mary knows a lot about, having worked for Harrods and Harvey Nichols.

Always interested in fashion, she thrives on the business of selling it and understanding why people part with their cash. "But I'm not obsessed by fashion - I think that's a bit worrying," she adds.

Her first job was designing and dressing the 'Way In' windows at Harrods, which happened to back on to the men's changing rooms. One day, Mary stepped out of the windows to find Mohammed Ali in his Y-fronts.

"It was a great experience to work at Harrods, really phenomenal - such a vast business that caters for everything," she says.

After that, in the early 1980s, she spent a year designing windows for fashion boutiques on London's Kings Road, including Vivienne Westwood and Malcolm McLaren's shop.

She joined Topshop before arriving at Harvey Nichols where she made a huge impact as creative director, including doing a deal with Jennifer Saunders to make the store the fashion empire in Absolutely Fabulous. And 10 years ago she started her own business, retail branding and communications agency Yellowdoor, which has created campaigns for brands including Clarks, Louis Vuitton, Oasis, Swarovski and Miss Selfridge.

So it is imperative to find out what Mary thinks of today's high street. What are the best shops out there? "I think that even though it gets bad press Gap has brilliant collections and very good service," she says. "Jigsaw has reinvented itself very well and Reiss is a very good retail shop. Oasis is a great little fashion business and Topshop is great. There are lots of people doing it well."

And the worst? "I have to be careful about this, but there are lots of bad ones out there."

In the past Mary has notably described Primark as making her "feel sick" .

She explains: "I just think bringing accessibly priced fashion to the masses is a good thing, it's very important. But how can the prices be so low? Someone, somewhere, is suffering. I also think it has killed the fashion season, and we don't actually need that much in our wardrobe. I genuinely don't think we need that much cheap fashion and we have to ask questions about what we are doing to the world with that level of turnover."

She has a similar opinion of supermarket fashion - "to me, selling fashion is about creating a fabulous place, about inspiration, about tactile stuff, the smell. It's about giving something special to consumers and I hate to see that done in any other way."

She commends Marks & Spencer for its efforts to refresh its stock and introduce new shopping opportunities.

She explains: "I love M&S for restoring our belief in it again and you can't underestimate that.

"The competition is so vast that the playing field has changed from what it was. The giants that led the way before have to be 10 times cannier now because there are so many people out there doing it and it's so accessible."

One way some stores have tried to attract customers is to introduce a specially designed line - whether the guest designer is a popstar, model or fashion designer.

"They are just quick marketing spins," says Mary. "Where there is a designer behind it can be fantastic, such as Karl Lagerfield designing for H&M which I loved. But where you've got a pop idol doing it, give me a break."

Mary believes that the essence of a great shop is that it must exude " fabulous" taste. After that, its atmosphere and interiors should entice customers to "hang out as well as buy". And, of course, superb service and expertise are essentials.

Sadly, these are qualities that are becoming the exception rather than the rule.

"With the growth of the multiples it is declining, terribly. As is real style advice in fashion," Mary affirms. As a shopping expert Mary naturally finds it easy to put her own wardrobe together and returns to the shops she knows do their job well.

Among her golden rules for shopping are to never put up with poor service and don't part with your money unless you really love the item.

While Mary has enjoyed outstanding career success, she says her priorities are her children, Mylo and Verity - illustrated by the time she told Giorgio Armani she was unable to make a meeting because it was Mylo's sports day. " When you put your family first then you're ok," she says.

"How do I manage everything? I just do, and don't beat myself up about it."

And her greatest achievements?

"Personally, having my children beyond a doubt," she says.

"Professionally, really it's not the big businesses but the small ones that I've been able to help that has given me a really warm, fuzzy feeling."