The Crown star took to the stage during a performance by Little Simz’s song “Introvert”, which features a verse recited by Corrin.
The actor wore a white blazer that featured a sheer lace veil for the appearance.
Corrin also wore a pair of black high-waisted trousers and an oversized white hat, a signature look in Reed’s designs.
Reed is best known for his gender-fluid designs, which champion individuality and sustainability.
The British-American designer’s clothing has been worn by the likes of Ezra Miller, Adele, Solange, and Harry Styles.
“The Harris Reed world is all about playing with ideas of gender,” Reed previously told The Independent. “People get so outraged by this idea of not wearing items that are ‘for their gender’, so this collection is all about toying with that and almost being quite tongue-in-cheek.
“People like to put others in boxes. When you tell someone that something doesn’t fit into a male or female binary, they don’t know how to react and compute that.
“So I think it took fashion a while because it’s a business and people were scared about pivoting towards gender-fluidity because you can’t make money from it. But hopefully, as brands like Gucci and myself have shown, that’s not the case.”
Corrin, who recently changed their pronouns on Instagram to she/they, has previously spoken about their gender identity.
“I think visibility is key with these things. I’ve felt it, because my journey has been a long one and has still got a long way to go. I think that we are so used to defining ourselves, and that’s the way, sadly, society works, within these binaries,” Corrin said in an interview with ITV News last year,
They added: “It’s taken me a long time to realise that I exist somewhere in between and I’m still not sure where that is yet.”
Corrin added that deciding to speak out about their queerness online was “scary and revealing” and that they “[weren’t] sure whether it was the right thing to do”.