A professional wrestler and actor has died after collapsing during a bout in London.
Cesar Barron, known as Silver King, was a star in his native Mexico and appeared alongside the comic actor Jack Black in the 2005 film Nacho Libre.
The 51-year-old was performing at the Roundhouse in Camden when he fell to the canvas.
A fellow Mexican wrestler paid tribute to his "great rival", saying: "He went as he wanted: fighting!"
El Hijo del Santo, aka Jorge Rodriguez, tweeted his "deep regret" at the death of his "partner in so many battles".
Barron had been in the middle of a match at the Greatest Show of Lucha Libre event on Saturday. Reports in Mexican media suggest he may have suffered a heart attack.
Roberto Carrera Maldonado, who attended the fight, said it initially looked like his collapse was part of the show.
"It felt like it was staged," he told the BBC. "Obviously it was quite normal in the fight."
But the wrestler stayed on the floor despite the referee's efforts to revive him. Footage posted online shows the referee and several other men coming to his aid after he collapsed.
"All of us were really shocked - it wasn't clear what was happening," Mr Carrera said. "I had the impression they didn't know what to do."
Mr Carrera said another fighter was pressing Barron's chest, and added that it seemed to be a long time after the wrestler collapsed before paramedics arrived.
The show was initially paused, but a loudspeaker announcement later asked the audience to leave.
Ambulance medics arrived five minutes after being called at 22:21 BST, London Ambulance Service said, adding: "Sadly a person died at the scene."
The Roundhouse confirmed there had been an "incident" during the show but said it was unable to comment further.
It later tweeted its condolences, saying: "Last night Silver King sadly lost his life during an event at the Roundhouse.
"At this stage the details are still being investigated so we don't have more information we can share."
Lucha Libre features masked competitors, or Luchadors, facing each other in acrobatic, choreographed battles.
Barron grew up in a Mexican wrestling family and his father was a popular lucha libre fighter.
As Silver King, Barron found worldwide success, appearing in the USA's World Championship Wrestling (WCW) from 1997 to 2000.
In 2005, he starred as the villain Ramses in Hollywood comedy Nacho Libre alongside Jack Black.
He reprised his role as the "evil Ramses" during Saturday night's performance.
Tributes have flooded in from the wrestling world, with US company WWE among those mourning the star.
WWE is saddened to learn that Lucha Libre legend and former WCW star Silver King has passed away at age 51. https://t.co/mAge65OmeN— WWE (@WWE) May 12, 2019
Former World Championship Wrestling (WCW) president Eric Bischoff said he was "saddened to hear about the passing of Silver King".
"Like so many of the great Luchadores that helped Americans appreciate Lucha Libre and make Nitro [a WCW flagship show] the success it was, he will be missed," he added.