Harry Style left the crowd stunned as he was unveiled as a surprise guest during Steve Nicks' headline set at BST Hyde Park on Friday evening.

The Water Melon Sugar singer, 30, joined the Fleetwood Mac icon, 76, as she paid an emotional tribute to late bandmate Christine McVie on what would have been her 81st birthday.

Christine tragically died in December 2022 after suffering a stroke as she battled against cancer.

Harry joined Stevie on stage for a perfomance of her classic hit Stop Draggin' My Heart Around and Landslide before she paid tribute to her later friend. 

The pop star oozed confidence as he took to the mic in his trademark 70s suit while Stevie was every inch the rocker in all black.  

As Harry watched on, an emotional Stevie told the audience: I want you to know that Christine was my girl and she loved all of us and today was her birthday'. 

'All of you have helped me get over [her death] and I want you to know how much I appreciate it'. 

Before telling Harry: 'Harry, I thank you, we thank you!'.

Stevie previously revealed the death of Christine put the final nail in the coffin of their legendary rock band Fleetwood Mac following five decades.

The classic line-up - including John McVie, Lindsey Buckingham, and Mick Fleetwood - performed for the final time together during their MusiCares tribute at Radio City Music Hall in Manhattan in 2018.

Shortly after, Buckingham was fired and replaced with singer-guitarist Mike Campbell and musician Neil Finn, who joined Fleetwood Mac for their 88-date An Evening with Fleetwood Mac tour in 2018-2019.

'We had a really great time and it was a huge tour. That was there in the realm of possibility,' the 75-year-old rock queen told Vulture.

'But when Christine died, I felt like you can't replace her. You just can't. Without her, what is it? You know what I mean? She was like my soul mate, my musical soul mate, and my best friend that I spent more time with than any of my other best friends outside of Fleetwood Mac.'

 Stevie (born Stephanie) compared her relationship with the British keyboardist-singer to Taylor Swift's 2022 song You're on Your Own, Kid where she wrote the line 'you always have been.'

'That was Christine and I. We were on our own in that band. We always were. We protected each other,' Nicks explained.

'Who am I going to look over to on the right and have them not be there behind that Hammond organ? When she died, I figured we really can't go any further with this. There's no reason to.'

Fleetwood Mc drummer said he was  still holding out hope that Buckingham and lead singer Stevie can bury the hatchet.

The co-founder of the band made a point of sharing that a peaceful resolution between the two former bandmates and lovers doesn't necessarily have to involve the reformation of Fleetwood Mac.

'It's no secret, it's no title-tattle that there is a brick wall there emotionally,' the British musician, 77, told Mojo of Buckingham and Nicks' rocky relationship that spans back to the 1960s. 

He added, 'Stevie's able to speak clearly about how she feels and doesn't feel, as does Lindsey. But I'll say, personally, I would love to see a healing between them – and that doesn't have to take the shape of a tour, necessarily.'