WHEN Frank Bruno climbs into the ring in Las Vegas tonight, he will be older, heavier, fitter and perhaps wiser then he was when Mike Tyson stopped him in five rounds in the same city seven years ago.

For all that, the Vegas book makers are unimpressed. The weight of money brought in by 5,000 British fans has whittled Bruno's odds to a still generous seven to one. It has been observed that the advantages which Bruno enjoys in terms of height and reach and weight are akin to the advantages which a zebra enjoys when facing down a lion.

Whether Tyson retains the same feral qualities which made him the most feared fighter on the planet back in the eighties remains to be seen. The old Tyson was a man of compulsive and uncontrolled appetites, who found in boxing a legitimate outlet for his need to inflict physical violence.

His appetites ultimately earned him three and a half years in prison and informed opinion around Las Vegas, where he has made a home, suggests that while he was away, Tyson figured out some things but not enough things. Either way he doesn't burn with the same uncontrollable rages. He seems trapped by boxing, resigned to the fact that the only way he can escape the fawning attentions of his own entourage is by climbing through the ropes.

Whether this diminution in Tyson's status as the most comprehensively frightening man on the planet is enough to enable an honest toiler like Frank Bruno to hit pay dirt early tomorrow morning seems unlikely.

In his two fights since his return from prison Tyson has scarcely been tested. Peter McNeeley's performance in the ring against Tyson was sufficient to render the phrase "fighting Irish" a contradiction in terms. Tyson's second opponent, Buster Mathis, made some claims to possessing the talents of an escapologist. Ducking and weaving got him as far as the third round while Tyson threw some wildly mistimed punches in the knowledge that one connection would finish the fight. It did.

It seems true that Tyson is somewhat less than a happy camper these days. Never known for his quick wit or easy flamboyance, his resentment of public scrutiny has been heightened by his confused sense of a general hostility directed towards him.

Tyson's lack of apparent public contrition since his release from prison has disturbed people on both sides of America's racial divide. It has been noted that prison appears to have taught Tyson the legal view of violence towards women but not the moral position. There is a strong body of opinion that Tyson's presence amongst the top ranked contenders is a severe embarrassment even to a sport as thoroughly soiled as boxing is.

To add weight to the rumours of his unhappiness, Tyson's two open training sessions in Vegas have ended disastrously. A lacklustre outing last Friday earned him an obvious rebuke from trainer Jay Bright, while Tuesday's session was cancelled entirely.

A resentment of the wider audiences who always feared and admired him without ever offering him genuine affection may be behind Tyson's poor public showings. Bruno's camp have been keen to grasp any argument which bolsters the case of their man. They point out, too, that the Mike Tyson who went to prison was already past his peak, his energies dissipated in a bad marriage and a generally disastrous personal life. It is six years since Tyson last fought a fight with a world title on the line.

However, for all the claims that he hasn't regained the fire or the sheer strength which made him such a savagely dangerous opponent before prison, Tyson still retains the explosive punching power and dogged panzer style attacking movement which made him the youngest world champion over some 10 years ago. The neck isn't quite as bullish and the muscles aren't quite as exaggerated, but his physique is still awesome.

One suspects, however, that to take advantage of a Tyson who perhaps only 70 per cent the boxer he was still requires mores talent than Frank Bruno has to offer. Seven years ago Bruno hit Tyson late in the first round with a clubbing arc of a shot with his left which Tyson pronounced as the hardest he had ever taken. The fact remains, however, that, Bruno hadn't the armoury to capitalise on Tyson's distress. Tyson recovered and battered Bruno into defeat by the fifth round.

Bruno claims with some justification that he is a better boxer now, stronger and wiser and a bit more versatile. This may be true, but the stiffness of movement, the lack of killer instinct and the suspect stamina over a long haul, still remain. On his bad days Bruno's head, held high and back, has always represented an attractive target for good punchers.

And on his bad days, let's face it, Bruno is very bad, his reactions and brain speed slowing down drastically, his stiff, slow body unable to take the necessary evasive action needed to aid recovery.

Bruno is four inches taller than Tyson and enjoys some advantage in the matter of reach. However, he is limited in the variety of punches he has available and depends excessively on a metronomic jabbing routine spiced occasionally with a solid left hook.

With regard to winning tonight, Bruno faces a gambler's dilemma which befits the venue. He needs to conserve energy for the possibility of later rounds and yet he must start well, as he did in 1989, and capitalise on what advantage he can accrue. His stamina has always been suspect and, tired, he will make easy prey for Tyson. Somehow he must find either the killer instinct to finish Tyson off early or the energy to stay with him through a gruelling fight. One suspects that neither option is available.

"It will be explosive," promised Bruno on Thursday after the weigh in. Tyson hooded and brooding, nodded silently and just smiled to himself.

The years may have withered Tyson slightly altered his perceptions of the world to a degree that he no longer sees boxing as being central to the core of his being. Stuck into the squared circle with a live foe, however, he still has enough of the old ferocity to prevail within the distance.