Watch the final minutes of bidding for Geri's Union flag dress

It was part of 88 lots of the singer's mementoes of her days from the Spice Girls, which raised thousands for a cancer charity.

The mini-dress was the highlight of a rock and pop souvenir sale at Sotheby's auctioneers.

Ms Halliwell, 26, promised to personally deliver the outfit and matching black corset.

Geri and the dress at the 1997 Brit Awards

When it came under the hammer, the dress was the subject of frenzied bidding.

It was originally rated at �12,000. But the bids shot up before Ms Halliwell slammed down the gavel at �36,200.

The buyer was Peter Morton, of Las Vegas' Hard Rock Hotel, who will pay �41,320, including a 15% buyers' premium.

He bid by telephone, beating rival bids from The Sun newspaper.

The Sotheby's sale marks the end of Geri's links with the Girl Power image of the past. Now she sports a fresh-faced, demure look, as she looks for work in film and television.

Sale for charity

A bit of Spice up for grabs

Ms Halliwell wants all the cash raised at the sale to go to the charity Sargent Cancer Care for Children. She had a benign lump removed from her breast at the age of 18.

After the sale, she said: "Thank you so much. I really appreciate this. I'm sure the children and all their families do as well."

The charity's chief executive Diane Yeo said: "Geri is a superstar, you can tell that the moment she walked into the room. I'm sure her presence at the auction has made a huge difference to the amount of money we've raised."

BBC Arts correspondent Rosie Millard: Bidders got what they really, really wanted

Other items sold include a 1967 MGB roadster which she bought with the proceeds of her first royalty cheque. It fetched �8,500.

An Elvis-style rhinestone-studded outfit worn to the 1997 Billboard awards fetched �4,140.

"Dreams more than fulfilled"

Auctioneer Kerry Taylor, who conducted the sale, said: "I think Geri still has her memories, and as she's not a particularly materialistic person, she would rather these things which she will no longer wear were sold for a good cause.

"We had never had a sale of this kind before and when we compiled the estimates we had our fingers crossed. But our hopes and dreams were more than fulfilled, we are delighted with the sale."

The 88 lots fetched a total of �146,511.

Other items which fetched large prices included a dress worn when the Spice Girls met Nelson Mandela, which went under the hammer for �3,680; and a pair of Stars and Stripes platform ankle boots, which made �2,990.

But not everything made the auctioneers' estimates. A revealing red dress worn to the 1997 Brit Awards was expected to fetch �6,000, but was sold for �2,300.