Nobody could accuse Dereck Chisora of ignoring the finer traditions of the fight game. Heavyweight boxing has had its share of volcanic characters – Mike Tyson, Oliver McCall and Herbie Hide in recent times – but Chisora gambled beyond his resources when he slapped the concrete slab masquerading as the chin of Vitali Klitschko at today's weigh-in for their world heavyweight title fight at the Olympiahalle.

The Finchley fighter, cool all week, boiled over in snowbound Munich on the eve of the biggest night of his life – and he picked the wrong family.

Chisora's fellow-Londoner David Haye went down this pot-holed road of theatrical pre-fight boorishness with Vitali's brother, Wladimir, in Hamburg last July (although he kept it verbal) and ended up on the end of the Klitschko jab for 12 rounds. Haye lost his WBA title and his dignity, a toe-curlingly poor exit from the big time. The Klitschkos really are as cool as they appear.

In the flash of a photo opportunity, Chisora has made a tough assignment immeasurably more difficult. "No one expected him to do that," his manager, Francis Warren, said. "It's not something we would condone." His trainer, Don Charles, said it was "unacceptable".

Klitschko was heard to say: "You're fucked now, Dereck, you are really fucked." He added: "I'll be hitting him back tomorrow, in the ring. He's not all there. Dereck is full of nervousness and I feel he is afraid, otherwise he would not have jumped back like he did. He hit me not like a boxer but like a woman, with an open hand. If he wants to fight properly, he must do that with his fists."

Chisora could face a fine of $50,000 (£31,600) from the World Boxing Council, whose president, José Sulaimán, described the slap as "an absolute disgrace".

If Chisora, 28 going on 12, a 17-fight novice with a big punch and surplus of adrenaline, thought he was going to upset a 40-year-old hard man going into his 16th world title fight with a sucker-tap to the jaw, he has been listening to the wrong people, or not listening to the right people. He is a law unto himself, which makes him dangerous – to himself as well as others.

No one really knows Chisora, a boy/man in search of an identity. He speaks Shona and north London wanna-buy-a-suit street. The kid who arrived in the UK from Zimbabwe aged 16 as a refugee from Robert Mugabe's bush wars collects old red telephone boxes, is saving up to buy a London bus, at least making him stand out among his neighbours on the Finchley fringes of the posh Hampstead Garden Suburb.

Like Trotters Independent Traders, "Del Boy" Chisora has taken the order but is yet to deliver.

He trades in enigma. He might kiss you or bite you, as he has done to opponents in the past, and, bored by the low-key ambience here this week, he thought about planting a smacker on the lips of the best heavyweight in the world. Instead, he chose a staged right-hander.

Chisora seems to be stranded between self-conscious menace and inner doubt. He would finish it in eight rounds, he said earlier in the week. "This is one cat who isn't scared of him," he said, trying to blank the champion, "or anyone." Klitschko was unmoved, the Titanic nudged by a pesky tugboat.

Friday's shot was a stiff one, but not enough to disturb Klitschko's Zen-like calm.

Chisora, nonetheless, is a puzzle to be solved and a fighter for rich title-holders to entertain largely because he comes cheaper than a dodgy blow-up doll. He is 17st 3lb of cut-rate chaos, 2lb lighter than the champion.

If, however, Chisora can land a proper blow on the Ukrainian behemoth on Saturday night, the gathering will rise in their uniquely German and unemotional appreciation of the fight game to acclaim the biggest shock in heavyweight boxing since Buster Douglas knocked out Mike Tyson in Tokyo 22 years ago.

That is the size of the challenger's task. In boxing's mountaineering argot, the Klitschko brothers represent K1 and K2.

If Klitschko has an off-night Chisora, who knows he may not pass this way again in a hurry, could be Johnny-on-the-spot. Except Klitschko does not do off-nights. Nor does he have many off-rounds, or even off-minutes. Since he returned to boxing in 2008 with rebuilt knees that gave up on him after he belted Danny Williams into painful, noble defeat four years earlier, Klitschko has dismissed seven opponents with the cold eye of a hit-man. As long as his body holds up (his back has troubled him and he has not trained at full bore for some time), he is the best – not quite as quick or skilful as his brother, but more intimidating by a stretch.

Lennox Lewis, who beat Klitschko on cuts in 2003 then frustrated him by walking away from boxing, says: "Coupled with their experience and skills, it's not surprising that [the Klitschkos] own the division. [The] competition is either too old, unconditioned or [too] young. I haven't seen enough of David Price, Seth Mitchell or Deontay Wilder to form a good opinion. As far as I know, they are good up-and-coming talent. Chisora has a chance, though."

While Chisora is gargantuanly unsubtle, a fighter not so much of craft as instinct, his will is immense. It dwarfs his pedigree and, some times, his discipline. Everyone else might sense doom but he is oblivious to it, and that is a strength. He also probably knows more about the mystery of boxing than its nuances and loves the story of how his hero, Muhammad Ali, spooked Sonny Liston the first time they fought (then did it again), beating his mind with his orchestrated craziness before breaking his spirit and body.

His favourite Ali line is one of the great man's least remembered: "People don't realise what they had 'til it's gone. Like President Kennedy – nobody like him. Like The Beatles, there will never be anything like them. Like my man, Elvis Presley – I was the Elvis of boxing." Chisora likes to think he is the Derek Trotter of boxing. Or will he turn out to be a plonker like Rodney?