“Vivien was a lady and a pillar of the anti-establishment.
Bold, creative, thoughtful and a good friend.
The best representative of Britain.
I and many others will miss her terribly,” Assange’s wife Stella Maurice wrote on Twitter, noting that the words belong to her husband.
Maurice called the British fashion designer "a true altruist" and accompanied the post with a photo of her wedding dress, designed by Westwood and Andreas Kronthaler.
In March, WikiLeaks founder Julian Assange married lawyer Stella Morris in Belmarsh, a maximum security prison in London.
The wedding was attended by six guests, including their sons Max and Gabriel.
Assange and Morris were engaged for five years.