It has been 30 years since it was worn in front of the world, but Princess Diana's wedding dress is still demanding attention.

While Catherine, the Duchess of Cambridge's wedding dress was watched by billions around the world on TV last month, Princess Diana's dress continues to be viewed by hundreds of thousands of people since her wedding day in 1981.

Even on April 29, as Diana's son Prince William married Catherine, the exhibition showcasing Diana's dress, complete with its 8m train, was a sell out in Kansas City in the US, the UK's Daily Mail reported.

The dress is currently part of an exhibition celebrating Princess Diana in the US and has been viewed by more than 1 million people.

Art handlers Graeme Murton and Nick Grossmark are currently travelling with the "priceless" piece around the globe and know every inch of the ivory silk taffeta and lace gown.

"It is simply magnificent, and the most famous dress ever. At the wedding it was seen by almost a million people," he said.

The exhibition, which showcases Princess Diana's full wedding dress ensemble, is part of a 150-piece exhibition called Diana: A Celebration.

But the wedding dress is by far the most difficult piece to transport in the collection.

Graeme and Nick are the only two people allowed to touch the dress and do so wearing white gloves. Every time the dress is moved it is covered in acid-free tissue paper and cotton fabric before being transferred on to a rolling cart and stored in a £3000 ($4564) foam-lined box.

Princess Diana's dress actually belongs to Prince William and Prince Harry and permanently lives at Diana's family home, the Althorp Estate and is looked after by her brother Earl Spencer.