Wladimir Klitschko has been warned that he risks being disqualified in his fight with Anthony Joshua at Wembley over his notorious 'jab and grab' tactics.
American David Fields has been appointed as referee for Saturday's heavyweight title bout, and several former officials who have overseen world championship fights have told The Daily Telegraph that he should warn Klitschko before the fight over his excessive use of holding. The tactic is illegal in boxing, but has become one of Klitschko's tactics for survival in the ring.
Former referee Joe Cortez, who officiated several of Klitschko's fights, said: "The referee has to take control in the dressing room - and excessive holding could lead to the fighter being disqualified. Those are the rules. Klitschko has to be very careful.
"If he has two points deducted for it, by the third time he could be disqualified. It's key that if he does do it, the referee must take points away early. Holding to gain an unfair advantage, just like rough tactics or pushing down, is not acceptable."
Klitschko has developed a technique of throwing his jab or double jab, and then - if he is unable to follow with his right hand - slides into range and ties up his opponents, leaning on them up close, or pushing them down, tiring them with his size and weight and making it impossible for them to throw punches.
Boxers down the ages have indulged in all sorts of dirty tricks, from low blows to punches to the back of head - known as rabbit punches - biting and butting, and using the thumb of the glove to an opponent's eye.
Pictures: the 'jab and grab' explained
"There are so many different ways of erring on the illegal and getting away with it," said the retired English referee Mickey Vann.
"Trainers taught you to tread on an opponent's toes, hold. When the referee said break, you ignored him. Then he would stop you boxing and he'd give you a warning and in that time you've got your head round a bit."
Klitschko's worst excesses came against Alexander Povetkin in 2013, when referee Luis Pabon allowed him to drape himself all over the Russian after almost every punch. No warnings or point deductions for repeated infractions made the fight a farce.
Vann suspects Klitschko could employ similar tactics against Joshua. "I would expect Joshua to win but if Klitschko is allowed to 'old man' him, he can get Joshua so frustrated that he's going to lose," he said. "He'll leave himself open and forget all about his game plan. If Klitschko's 'jab and grab' goes on for six or seven rounds and the referee doesn't do anything about it, there is a danger that Joshua will say 'balls to this - it's do or die'.
"The referee is very important. Not just for the safety of the fighters but he can guide a fight along one way or the other. It depends on how strong the referee is."
Vann recalled the Lennox Lewis-Frank Bruno fight he oversaw for the WBC heavyweight crown in Cardiff in 1993. "When I refereed Bruno against Lewis I knew Bruno was going to do the same sort of thing. I jumped on him straight away. I didn't do it in the proper way. I knew what he was going to do and I thought I'm going to shock him. I didn't use the best of language. What I said to him was industrial language, but it did the job. I stopped him using illegal tactics."
Richard Steele, who oversaw 167 world title fights and caused a near riot when he stopped the contest between Mike Tyson and Donovan Razor Ruddock in the seventh round in Las Vegas in 1994, believes Joshua's size and strength will make it difficult for Klitschko to employ his underhand tactics.
"I don't think Joshua is going to allow Klitschko to grab him," Steele told The Daily Telegraph. "Muhammad Ali got away with it, George Foreman got away with it, the Klitschkos have been getting away with it. But it's still up to the opponent to protest or try to fight.
"If the opponent is not fighting back, and not trying to punch, the referee's hands are tied. He's got to show some resistance. That he doesn't care for him holding him or grabbing him. It makes the referee have to make a decision on whether to take a point away or give a couple of strong warnings and then take a point away.
"He won't allow him to jab and grab. He's a tremendous fighter, a tremendous athlete, and he has the youth and the speed to move and stay out of the way of him grabbing. I haven't seen a young guy with so much talent with the right attitude for a long time."