Newly-crowned WBO light-heavyweight champion Nathan Cleverly lit the touchpaper for Saturday's grudge match with domestic rival Tony Bellew in an explosive press conference which saw the pair nearly come to blows.
Cleverly will face Liverpudlian Bellew after Juergen Braehmer, who he had been set to challenge for the WBO belt, pulled out of the O2 Arena bout and was stripped of his title.
Cleverly was subsequently upgraded from 'interim' champion, and for his first defence promoter Frank Warren gave a chance to unbeaten Commonwealth champion Bellew.
The two are long-time rivals and sparks flew when they came face-to-face in London on Thursday.
Bellew arrived at the press conference late but immediately started insulting Welshman Cleverly and security guards had to intervene as the banter turned nasty.
"I'll give you a free punch," Cleverly taunted.
Hot-tempered Bellew reacted, threatening to put the Welshman "in an ambulance", spitting expletives and repeatedly calling Cleverly "a f****** rat" when the champion offered to take the matter outside. Security guards then had to step in to physically pull the two men apart.
Cleverly, who had some choice obscenities of his own, said: "He is not as good as Braehmer.
"Braehmer was the champion, he was proven.
"But I'll only call myself the world champion when I win on Saturday night."
It emerged yesterday that Braehmer was not going to defend his belt, citing an eye injury, and Warren then lobbied the WBO to strip the German of his title and name Cleverly champion while beginning the search for a credible replacement opponent.
Bellew, ranked in the WBO top 20, jumped at the chance, while the governing body granted Warren's wish overnight.
Bellew, 28, needs to lose a significant amount of weight to make the 12st 7lb limit having taken the fight at late notice.
"The weight is not an issue," said the challenger. "I've met the board's requirement and it doesn't matter whether I get 24 hours' notice, 24 days or 24 months, I'll knock him out."
Warren told Press Association Sport: "Once he has the test weigh-in, hopefully everything will be confirmed.
"We've got nearly everything done that we need to do.
"It's funny because it's gone from a fight that hardly got a mention because all everyone was talking about was the George Groves and James DeGale fight and now we've got two fights that they are all talking about."
Both Cleverly and Bellew are unbeaten Warren prospects and the promoter admitted: "I'll be very honest and admit that I'd prefer these two guys not to be fighting at this stage.
"I would have liked to have built it up a bit more but he (Bellew) wanted it, he said he'd been in the gym - which we know he has been, because he lives a good life - and it is what it is.
"The fight between Nathan and Tony has been brewing up in the last year and it's happened sooner than expected but I'm delighted that the fight is on and the fans are in for a real treat on Saturday night.
"There is nothing like big domestic fights and in this case on Saturday at the O2 we have two big title fights involving British guys and I'm expecting fireworks in the ring."
Cleverly, 24, has garnered more attention in recent years due to his rapid rise through the sport while studying a mathematics degree which he completed last year.
But Bellew is a talent himself and despite wobbles in recent performances, the Liverpudlian remains unbeaten and has a reputation as a powerful puncher.
Bellew (15-0, 10KOs) had been training for a July rematch with Ovill McKenzie anyway and said: "I'm going to knock Cleverly out cold.
"I wouldn't have put myself forward if I didn't think I could beat him.
"Be it two months' notice or two days' notice, I know I can beat Cleverly - I always have. For the fans, I can promise them the best fight they will see in the last 10 years."
The news adds spice to an already solid card in London, with Cleverly (21-0, 10KOs) sharing top billing with the much-hyped British and Commonwealth super-middleweight title clash between DeGale and Groves.