David Haye appeared to throw a punch at Tony Bellew during a bad-tempered press conference for next year's grudge fight.
The bitter rivals will meet at The O2 on March 4, live on Sky Sports Box Office, and Haye seemed to aim a blow at Bellew as tensions boiled over when they posed for pictures.
Security staff quickly stepped in to separate the feuding pair before they could become embroiled in a physical confrontation.
Haye had earlier mocked the Liverpudlian by claiming he could knock out Bellew while "drunk out of my head".
"You and your whole team are going to get destroyed," said Haye.
"Whatever I do now in my life is irrelevant because on fight night, you're going to get knocked out.
"I could go clubbing every night. From now until the fight... get smashed out of my mind every night, and I'll still knock you out.
"I will turn up, drunk out of my head, and you'll get knocked out."
Bellew is the current WBC cruiserweight champion, but suggested he had to agree to a number of demands from Haye before the fight was finally made.
"I don't fear him," said Bellew. "He's got this thing that I'm scared of him. All those demands, all those stipulations you put in.
"'I want the ring this size, I want the mat that size'... Listen mate, I'm not going to run from you. I know you believe I'm going to run.
"All these stipulations he put in, I'm surprised he didn't ask me to carry him to his seat in the press conference, to be honest.
"Do you want me to do your hair as well? The man is unbelievable. My demand was - let me pick my own gloves and get in the ring.
"He's unbelievable - the biggest diva in boxing I have ever seen."
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