The 45-year-old who still calls himself Donny is being reborn in the UK, in front of several thousand women who have serious designs on his well-preserved self.
Considering that his solo career dates back to 1972, it seems impossible that this is his first British solo show - but, apparently, it has taken him until now to feel confident about playing without his brothers and Marie.
As he tells us, he has had his ups and downs - that bad time in the late 1980s when he tried out leather and stubble was a distinct low - but he wants to wipe the slate clean and start again.
That's not going to happen if the still-rapacious fans have any say in the matter. The deal between the audience and Donny is that they pay £28 a ticket and he sings the hits. He may weight the evening in favour of his new album - covers of "classic love songs" such as the Detroit Spinners' Could It Be I'm Falling In Love?, which opens the show - but it's the 1970s stuff that hits home.
"He's so lovely!" groans the woman in the next seat, whose father wouldn't let her see the Osmonds in Liverpool in 1972. Tonight is the culmination of a dream, she says, during a video excerpt of the white-jumpsuited teenaged Donny singing Go Away, Little Girl.
If you squint a bit, the difference between Osmond at 15 and 45 isn't that great. The teeth are still much in evidence - and so is the slippery dancing, which happens from the waist up. The only signs that it is 2003 are his black polo-neck and a bemused expression as he whisks through Puppy Love and Love Me for a Reason. He doesn't disown the old songs exactly, but it is obvious there is a frustrated R&B singer in that lightentertainer body.
Witness the zest with which he addresses Stevie Wonder's I Wish and the bizarre Crazy Horses - with a howl of "Oooeee!", he jerks across the stage like his old rival Michael Jackson. Skidding to a halt, he hangs onto the guitarist's shoulder, loudly urging her on. Either Mormon Donny has been supping forbidden Coca-Cola or he's enjoying himself. Sweet.
But how will it play in Vegas?
· Repeated tonight. Box office: 0870 606 3400.
