Magician is critically injured on stage as tiger leaps at his throat

It was not until the white tiger gripped the magician by the neck and dragged him off stage 'like a rag doll' that the audience at the Siegfried and Roy show realised this was no illusion

There are some magicians for whom any risk is just an illusion. Not Siegfried and Roy; for on Friday one half of this, Las Vegas's most spectacular and high-camp double-act, was critically injured when a white tiger suddenly leapt at his throat and dragged him off the stage "like a rag doll". Roy Horn may live, but this act will never be the same again.

Siegfried and Roy are the Liberaces of the magic shows and, like him, they have always lived dangerously. But unlike the bouffant-haired, rhinestone-encrusted old trouper, the duo's dangers, involving tigers, lions and other big cats, have always been more palpable and immediate.

They hid it well, developing a showy spectacle that has been a staple in Las Vegas for three decades, but always there was the risk that one day a lion or tiger born with less of an instinct for show business would strike without warning.

On Friday night, amid the glitzy stagings of the Mirage Hotel, it finally happened. Roy Horn, the dark-haired half of the duo, who was celebrating his 59th birthday, was 45 minutes into the act and led from the wings one of their trademark white tigers. It was called Montecore, a seven-year-old male, and it was making its debut. Cue renewed applause.

Whether it was that cascading noise, which the animal was hearing live for the first time, or just a rogue moment, but the tiger suddenly lunged at Horn. He tried to beat it off with a microphone, as the audience, half of whom thought it was part of the act, was transfixed. But when the tiger pulled Horn off stage they knew that the illusionist was being seriously, perhaps fatally, attacked.

Horn was reportedly able to speak with medics as an ambulance took him to hospital, but the animal had inflicted a fearful injury to the side of his neck. He underwent immediate surgery and was later said by his long-time manager Bernie Yuman to be in a "critical but stable condition". He added: "At the end of the day, when you perform that many shows and have no incident whatsoever, this is an anomaly."

It is also a tribute to their skills, for both Siegfried and Roy have worked with dangerous animals for no fewer than 44 years. But then neither has ever known a life without ever-present risk. Indeed, they were born into danger; both in Nazi Germany, both with childhoods blighted by the war, and both with alcoholic, disturbed fathers. Magic tricks were Siegfried Fischbacher's escape, animals Roy Horn's ­ even then he was drawn to the ones that packed a threat: his pet was a wolf-dog, his pastime helping clean cages at Bremen Zoo.

In 1957, when he was 13, Horn got a job as a bellboy on a German cruise ship, the Bremen. Already on the ship's staff was Siegfried, five years his senior, who enlivened his stewarding duties by performing magic for the passengers. Roy had a suggestion: instead of making a rabbit disappear, why not a cheetah? Siegfried, probably on the assumption the cabin boy was in no position to supply one, agreed.

Little did he know. And little did Bremen Zoo know who was responsible when, towards the end of Horn's next shore leave, they counted their cheetahs and found one missing. Within days, the animal was on board the Bremen, all set to be the newly formed Siegfried and Roy's first co-star. All three were a hit, and the cheetah was well-behaved, much to the relief of the Bremen's understandably anxious captain.

For the next few years they and the cheetah worked the ships, and clubs in Germany and Switzerland. In 1966 they performed before Prince Rainier and Princess Grace in Monaco. It was the first time they made a wider impact, not least because at the end of his trick, the cheetah leapt from the stage and headed to where the royals sat. Unpleasantness was avoided and the pair began to play big-time venues like The Lido in Paris.

They first appeared in Las Vegas, the city that was to become their stage and spiritual home, in 1970. Gradually they added more and larger animals to the act: lions, leopards, panthers, elephants, and white tigers. These, and the white lions they also use, now form the high spots of their show. The climax is a floating illusion with a white tiger appearing from a flaming silver ball. It jumps on to the ball, Roy leaps on the tiger's back and, then, at Siegfried's word, they are floated off into the air as the ball spins. This combination of magic, animals and lavish staging with dozens of costumed dancers is why audiences are prepared to pay $90 (£55) a ticket, and why the Mirage was prepared to sign a lifetime contract with the duo in 2001. As a result, their earnings are astonishing: $58m in 1997 alone.

This has not only enabled them to fund a mansion called Jungle Palace on an eight-acre spread west of Vegas, but also to plough money and time into conservation. They have bred nearly 50 white tigers and worked with zoos worldwide.

Siegfried and Roy have always refused to discuss their sexuality, but that has not stopped them becoming considerable gay icons. This is not something they have gone out of their way to discourage. Last year the two opened a new wing at the Liberace museum, arriving in one of the pianist's open-top pink Rolls-Royces and cuddling a white tiger cub.

Liberace was a man whose dangerous living was done behind closed doors. Siegfried and Roy's has been done on stage over five decades. There will be some who will see Friday's attack as the inevitable consequence of playing with the big cats. But Roy Horn and his partner have done more for these rare animals than all of their armchair critics put together. They are showmen, and they knew the risks.

When animals turn

* 1994: TV cameraman mauled to death by tiger during attempt to move starving animals from Angola to South African zoo.

* 1995: Elephant tramples keeper to death in Belgian wildlife park.

Romanian child killed by two bears during school zoo visit.

* 1997: 17-year-old boy dies after being attacked by lion at Sri Lankan zoo.

Four-year-old boy savaged to death after circus lion breaks loose in Brazil.

* 1998: Five-year-old boy mauled to death by a jaguar which had escaped from its cage at French zoo.

* 1999: Game warden killed by lions on safari ranch in Namibia.

* 2000: Keeper becomes second person killed by elephants at zoo owned by the late John Aspinall. Three others had been killed by tigress.

Young British tourist killed after elephant runs amok in Thailand.

* 2001: Egyptian sheep pushes owner to his death from building in Alexandria.

Keeper attacked by elephant at Chester Zoo. Dies 12 days later in hospital.

Egyptian Bedouin shot dead by sheep which kicked his gun, causing it to fire.

Czech zoo-keeper dies from elephant attack while attempting an injection.

Keeper at London Zoo trampled to death by elephant.