Interest in the dress - which was originally intended to be a skirt worn over a slip - reflects the furore surrounding every outfit Kate has worn in public since her engagement was announced - and even before.
The black and turquoise knitted silk tube, made by University of the West of England fashion graduate Charlotte Todd, was the highlight of today's central London auction as Kate-mania sweeps the world ahead of the royal wedding.
Before the bidding started auctioneer Kerry Taylor, who had valued the dress at £8,000 - £10,000, described it as the slip that 'caught a prince's eye and then his heart.'
She added: 'I am quite astonished by the amount of interest from all over the world, from Korea to Japan to America.
'Literally, there's global interest in the dress and that reflects the interest in Kate Middleton.'
'I feel quite sorry for her - if you're getting this kind of response to a dress that she wore for 10 minutes all those years ago, it's quite extraordinary.
'But we've not had Prince William on the phone yet. I'm very disappointed,' Taylor joked.
She had started the sale at £20,000 and, for a few minutes, took ever-increasing bids made by phone via staff who sat along one side of the sales room.
But when the price reached around £50,000, the battle for the dress turned into a two-way tussle between the man at the back of the room and some bids pre-registered with the auctioneer.
When the figure hit £65,000, Taylor waited a few moments before ending the auction to applause from the many buyers in the room.
The dress was one of 250 lots including including a Zandra Rhodes gown and a Catherine Walker formal white number, both worn by Princess Diana.
Charlotte Todd, 31, has watched the value of her dress - which cost her just £30 to make - soar ever since the couple got together.
Immediately after the announcement of William and Kate's engagement, Todd turned down an offer of £1,000 for the dress and vowed to hold onto it forever.
Now, with the royal wedding just over one month away, it seems that the temptation of an £8,000 - £10,000 valuation was just too good to resist.
Todd's official excuse for declaring that 'the moment is right,' though, was that the dress is so fragile, the responsibility of looking after it was just too much.
The dress had been sitting in a box at her parents' house for the past eight years.
Todd said of her creation: 'If it is true that my design helped change the prince's interest in Kate from platonic to romantic as has been reported, then I am pleased to have played a part - however minor.
'I never would have imagined as I sat knitting this piece that one day it would be so important.'
After the sale, Todd said: 'I'm completely shocked, I need to sit down and get my head round it.
'I just wanted to get out and get some fresh air during the sale. I wasn't expecting it. I was turning round to see who was at the back of the room and what was happening.
'"But I didn't like to get my hopes up, I was thinking it might not sell. I wasn't thinking of a sum of money in my head.
Asked what she would do with the money, Ms Todd, who was joined by her husband, Ric Brady, 26, who works in a coffee shop, and her mother, Liz Todd, said: 'We will probably put it towards a house because we're still renting.
'Maybe a change of career, maybe I should rustle up some more dresses?'
It is estimated that the see-through creation could be worth up to £100,000 when Kate becomes Queen. So perhaps Nick from Jersey's £78,000 was £78,000 well spent after all.
Kate Middleton
Kate Middleton
Kate Middleton
Kate Middleton
