LONDON • Justin Bieber is not shy over showing his love for his "queen" in public.

On Tuesday, he whipped out his guitar outside Buckingham Palace in London to play busker and serenade model Hailey Baldwin, whom he reportedly married in New York last Thursday.

The song he chose was Cold Water, his 2016 tie-up with Major Lazer and MO, People magazine reported.

Bieber, 24, who was also cheered on by a small group of onlookers, used to busk in the early days of his career.

The couple were in the British capital, where Baldwin, 21, had a modelling assignment in an Adidas fashion show.

But the pair also found time to enjoy the city's charms, including visiting the London Eye and walking along the Thames river to admire Big Ben, with eyewitnesses saying they displayed plenty of affection with hugs and kisses.

Her London catwalk outing has been a rare one for Baldwin, with Harper's Bazaar reporting that she cut back on her New York Fashion Week work recently to spend more time with Bieber.

But confusion still reigns if the pair are really married, despite media reports of the duo showing up in the New York Courthouse Legal Bureau last week.

Baldwin tweeted the next day to say "I understand where the speculation is coming from, but I'm not married yet".

However, Billboard magazine cited her uncle, actor Alec Baldwin, as saying on the red carpet at Monday's Emmy Awards: "They just went off and got married."

Bieber has not poured Cold Water over the speculation, tellingly confessing outside the palace: "And if you feel you're sinking, I will jump right over/Into cold, cold water for you."