When she was still Kate Middleton and a student at St. Andrew's University in Scotland, Kate decided to model in a charity fashion show in 2002. Prince William was in the audience.

The 19-year-old future Duchess of Cambridge walked down the runway in a see-through black slip with turquoise trim at the top and bottom by Charlotte Todd. Kate wore black underwear and a black bandeau bra under it. It was supposed to be a skirt, but Kate chose to wear it as a dress. 

It only cost £30 to make, but it was worth £10,000 after the engagement announcement (and was more in the future) according to its designer who admitted to the Daily Mail that it has been in the back of her closet ever since. 

The designer is pictured with the famous dress above before an auction. The dress ended up selling for $125, 871 to an anonymous buyer. 

The slip caught the Prince's eye in the audience and reportedly, their relationship started soon after. They had been friends, but he saw her in a new light after the fashion show. Reportedly, she was dating her first university boyfriend Rupert Finch at the time, and after their breakup, she began dating William. The rest, as they say, is history!