Watch Justin Bieber serenade Hailey Baldwin outside Buckingham Palace

He played 'Cold Water' and Tracy Chapman's 1988 hit 'Fast Car'

Justin Bieber was spotted singing to his partner Hailey Baldwin outside Buckingham Palace in London yesterday (September 18).

The ‘Sorry’ singer performed acoustic versions of ‘Cold Water’, his 2016 collaboration with Major Lazer and , and Tracy Chapman’s 1988 hit ‘Fast Car’ in front of Baldwin and a crowd.

Watch footage of the performance below.

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JUSTIN BIEBER OMG @justinbieber @haileybaldwin

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Baldwin filmed Bieber’s surprise performance as people gathered round to watch.

The couple had been sightseeing in London, and were also spotted near the London Eye. Baldwin, a 22-year-old model, had been participating in a catwalk show during London Fashion Week.

Rumours are rife that Bieber and Baldwin are now married, after Baldwin’s uncle, actor Alec Baldwin, confirmed the news to reporters at Emmy Awards on Monday (September 17).

But Baldwin denied the rumours on Twitter in a now deleted tweet, writing: “I understand where the speculation is coming from, but I’m not married yet!”

Justin Bieber and Hailey Baldwin deny they're already married

Hailey Baldwin and Justin Bieber

Bieber, 24, confirmed his engagement to the model and daughter of American actor Stephen Baldwin on Instagram in July, describing Baldwin as “the love of my life.”

In other recent news surrounding the pair’s engagement, Post Malone offered to perform for free at their wedding.

The rapper told TMZ in July: “I would love to perform – fuck yeah for free.

“I’ll be the flower boy or is that the ring bearer?” he continued. “He’s very happy and I love to see my boy happy.”