Fashion Guru Mary Portas returns to our Screens on Tuesday BBC2 9pm this time in the back rooms of charity shops, rummaging through bin bags of filthy, cast-off clothes.

It’s the last place you’d expect to find the glamorous 48-year-old, who’s credited with making London’s Harvey Nichols the shopping destination of every fashionista in town.

But now the lady who helped out-of-touch clothing shop managers transform their stores in the first two series of her hit show Mary Queen of Shops, is on another mission.

She’s aiming to transform the fortunes of the nation’s charity shops in just five months.

It’s a brave move. Donations to the shop include soiled babies nappies, and the over-60s volunteer staff are more interested in a good natter, than helping their customers.

Never one to avoid confrontation, Mary whips the ladies and their shop into shape with her well-honed brand of honest management.

“I have long wanted to get my teeth into the charity sector and, given their ethical and eco-friendly nature, I believe there’s no better time to give charity shops an overdue makeover.”

“I was shopping in one local to me in Notting Hill and these lovely women were having a chat. One was saying, ‘Shall I put the kettle on?’ and the other was saying, ‘Yes, mind the plug, it’s a bit dodgy’. All the rules of retail went out the window.

“They were in this little intimate world of their own. I just found it so entertaining and I thought, ‘My God, imagine if we put a system into these sort of businesses’.”

Her challenge – to get more people through charity shop doors and encourage better quality donations – is a tough one.

“When you look at most charities, the shops are not where they make their biggest money; their biggest money’s in the big fundraising events, so shops are low down their priority list,” she explains.

“I just genuinely think that charities don’t see retail as a huge opportunity.”

Mary takes her campaign to London Fashion Week, where she ropes in Peaches Geldof and Erin O’Connor to model charity fashion – as styled by her OAP volunteers.

“People have bought disposable, very cheap fashion for the last 10 years and thought that was clever. But we know now that stuff just ends up as landfill. It’s made incredibly cheaply and there’s someone somewhere suffering. That practice is not good for our world.”

During June, Mary will be opening her own charity shop in London’s new Westfield shopping complex, called Living and Giving.