LONDON (REUTERS) - Hollywood star Johnny Depp, awaiting a ruling in an American defamation case involving his ex-wife and actress Amber Heard, made an unscheduled appearance at London's Royal Albert Hall on Monday (May 30) during a rock concert, his second in as many nights.

The Pirates Of The Caribbean (2003 to 2017) star appeared with English guitarist Jeff Beck to perform a series of music covers, including former Beatle John Lennon's Isolation, a track they collaborated on and released in 2020, in the northern English city of Sheffield on Sunday, surprising the crowd.

On Monday, Depp showed up again onstage with Beck, at the iconic Royal Albert Hall, again playing Isolation among other tracks.

Jurors in Virginia deliberating the defamation claims from both Depp and Heard adjourned on Friday without returning a verdict.

They will resume discussions on Tuesday after the United States Memorial Day holiday. Beck is scheduled to have another show at the Royal Albert Hall on Tuesday.

Depp, 58, sued Heard for US$50 million (S$69 million), arguing that the Aquaman (2018) actress defamed him when she called herself "a public figure representing domestic abuse" in an opinion piece she wrote.

Heard, 36, counter-sued for US$100 million, saying Depp smeared her reputation when his lawyer called her accusations a "hoax".

Depp's fans took to Instagram and Twitter to share their views of the American actor's performance on stage.

"Johnny is an absolute mad man ... leaves court Friday .. playing a gig in Sheffield UK Sunday.. with Jeff Beck..mind blown," Twitter user @OneloveEarth said.

On Instagram, @flokpedals wrote: "Wasn't expecting this… I thought he was in court but turns out he's in Sheffield with Jeff Beck."

However, amid the online furore, some concert-goers were less than impressed.

"I felt duped. Totally 100 per cent duped. I had been waiting 50 years to see Jeff Beck live... this was the biggest letdown of my life," Mr Peter Schmidt, who had come from Frankfurt to London for the concert with his family, told Reuters outside the London venue.

"(Depp) took over the show, he shouldn't have been there. He is an embarrassment... I went to see Jeff Beck tonight, not a Hollywood star."