She actually wore the dress for the first time in 2008, when she attended a pre-BAFTA Awards party.
However, in 2014, the dress was nearly ruined when one of her friends accidentally spilled red wine all over it.
Keira told the Telegraph, “It’s quite impressively splattered. But, hey, a good night is a good night, and when a dress has had its time, maybe it’s had its time. I’m pretty sure I can get it out but, if I can’t, I’m happy with the memory of a good night and the story of how the dress got destroyed.”
Source: https://www.buzzfeed.com/kristenharris1/celebs-rewore-wedding-dresses