Kate, 28, modelled the dress at University Of St Andrews fashion show eight years ago, with Prince William mesmerised in the front row.
'The dress is a part of fashion history - the moment William could first have fallen in love with Kate - and that makes me really proud,' says the designer of the dress, Charlotte Todd.
'If it hadn't been see-through, William might not have noticed her.
'I definitely think it has played a part in the royal love story.'
Charlotte says she would never sell the dress, which she actually designed to be worn as a skirt, despite auctioneers telling her it's worth £10,000 and one day could fetch ten times that.
'The only person I'd probably give it to is her - maybe in exchange for a wedding invitation,' Charlotte tells the Daily Mail.
'Of course I would love to design her wedding dress too.'
Wills, 28, proposed to Kate on holiday in Kenya. The couple will marry on 29 April next year.
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Esme Riley
