Watch Stevie Nicks and Harry Styles Perform Together in London

Stevie Nicks brought out a special guest at her concert on Friday night at Hyde Park in London: Harry Styles.

When Nicks appeared for her encore, she performed "Rhiannon" and then introduced Styles who joined her for "Landslide." It was dedicated to Nicks' late Fleetwood Mac bandmate Christine McVie, who would have been celebrating her 81st birthday.

"At the end of the show, since the end of last year and since Christine passed away, I would say something about her, and I asked Harry to do this with me and it's a lot to ask someone to sing a heavy song about a best friend that died so suddenly and so sadly," Nicks said. "What I want to say to you is that Christine was Harry's girl, she was my girl, she was your girl, and she loved all of you, and today would've been her birthday, so, it’s taken me all this time to try to deal with this situation."

Styles stayed on stage for the final song of the evening, "Stop Draggin' My Heart Around," originally recorded by Nicks and Tom Petty.

Both songs are available for viewing below.

"One thing my mom used to say to me when I was little, when I was hurt, was 'Stevie when you're hurt, you always run to the stage,'" Nicks also said. "And that's what I have been doing ever since Chris passed away, I've been running to the stage. And the only people who have helped me to get over all of this, has been all of you."

Mick Fleetwood's Own Struggle

Nicks' bandmate Mick Fleetwood has also spoken publicly about the difficulty of McVie's passing.

"It's been a strange time for me," he told Mojo earlier this month. "Losing sweet Christine was catastrophic. And then, in my world, sort of losing the band too. And I split with my partner as well. I just found myself sort of licking my wounds."

Watch Stevie Nicks and Harry Styles Perform 'Landslide'

Watch Stevie Nicks and Harry Styles Perform 'Stop Draggin' My Heart Around'