July 22 - It was the best kept secret of the royal wedding, but now the Alexander McQueen dress worn by the former Kate Middleton when she married Prince William is being put on public display for all to admire.

Caroline de Guitaut, curator of the exhibition display adjusts the wedding dress of Catherine, the Duchess of Cambridge, at Buckingham Palace, in central London. - photo: afp

Catherine's ivory and white satin-gazar dress, designed by Sarah Burton, goes on show at Buckingham Palace on Saturday as part of the annual summer opening, where hundreds of thousands of visitors are expected to flock to see it.

One million people lined the streets of London to see the couple, now titled the Duke and Duchess of Cambridge, marry on April 29, but few will have got close enough to appreciate the intense effort that went into the stunning gown.

The lace applique on the bodice and skirt was made by cutting out individual lace flowers and sewing them in a unique design onto ivory silk-tulle, using tiny stitches every two or three millimetres.

Members of the Royal School of Needlework washed their hands every 30 minutes as they worked to keep the lace pristine, and changed their needles every three hours to keep them sharp.

In a video interview played at the exhibition, Burton explains for the first time the ideas behind the dress, in which Catherine herself was said to have been closely involved.

"We wanted to look to the past, yet look to the future as well," says the designer, who was long tipped for the coveted commission but was only confirmed by palace officials when Catherine emerged wearing the dress on the day.

"There were a lot of references to Victorian corsetry, the padded hip, the tiny cinched-in waist, and also to the arts and crafts movement with all of the hand-work on the lace of the dress and also the bustle inside to create the shape of the back of the dress.

"It has an essence of Victorian but we cut the dress in a very modern way, it is in a very light fabric, also the pleats and the folds create a modern feel rather than a historical piece."

The wedding dress of Catherine, the Duchess of Cambridge, is pictured at Buckingham Palace. - photo: afp

Burton said the aim was to create "something that was incredibly beautiful and intricately worked" but which would also not be lost in Westminster Abbey, the 13th century gothic cathedral where William and Catherine wed.

The dress, which had a skirt with arched pleats and a 2.7-metre (8.8-feet) train, was a "real feat of engineering", she added.

The exhibition organisers are expecting huge interest in the gown, which is being shown alongside Catherine's shoes, her diamond earrings and the "Halo" tiara she borrowed from Queen Elizabeth II to hold her silk-tulle veil in place.

The handmade ivory duchesse satin and lace shoes from the team at Alexander McQueen, a UK size 5.5, show slight signs of wear and tear.

Sales for the summer opening are already double what they were this time last year, with 125,750 advance tickets sold so far, a spokeswoman for the Royal Collection said.

Although a ticket includes access to a Faberge exhibition, Buckingham Palace's 19 state rooms -- including the ballroom where part of the wedding reception was held -- and the garden, the gown will be the highlight for many visitors.

"The dress is obviously a big draw. We are expecting a very busy summer," the spokeswoman told AFP.

The summer opening at Buckingham Palace runs from July 23 to October 3. Last year it attracted 413,000 visitors, but has capacity for 643,000.

by Alice Ritchie