They descended on to the Odyssey stage under a cloud of mauve dry ice to the accompaniment of shrieks and sighs from 4,500 mainly female fans.
That's what pop royalty is supposed to do and Donny and Marie, now incredibly 55 and 53, remain king and queen of the tooth-gratingly sweet three-minute pop song — not to mention Earth’s most famous Mormons according to Google (sorry Mr Romney).
The super-fit siblings swung into It Takes Two like the pros they are, but from the start there was a lack of back-up. This was a bit of an austerity variety show, to be honest, with a grand piano, the odd guitar (some very odd guitar when it came to the Crazy Horses solo), drums and keyboard. And a few dancers.
We were back in the 1970s, not so much Life On Mars as life on planet Osmonds, which was squeaky clean and given to promoting the idea that the family that sings together succeeds.
Although the Marie and Donny brand has cracked Vegas, musicals and tours, you do miss the other Osmonds. This original boy band was really hot back in the day and during Donny's wonderful Love Me For A Reason, his brothers emerged onscreen to create something memorable. Eat your heart out, Mr Barlow.
While American wholesomeness remains the Osmonds' shtick — life, liberty and the pursuit of perfect dentistry — there’s a nice amount of sauciness and both Donny and Marie made a point of getting into the audience.
Musically, the Osmonds really could write songs, even if you might not want to admit to owning too many. As Def Leppard’s Joe Elliott once said, Crazy Horses is a good song but he had to take it home in a brown paper bag. When Donny ripped into the opening bars with its rock, Deep Purple-ish hook, you knew what he meant.
What was fun throughout the concert, though, was the reactions of Team Donny, who are nothing if not committed.
When he sang a number from Joseph and came to the line, ‘Do what you want with me', they went wild, whooping like their teenage selves. He handled the adulation well, but he's used to it.
Marie attempted Nessun Dorma with two dancers in the dry ice ruining the seriousness. She had silenced the arena earlier with an emotional take on Lloyd Webber's Pie Jesu, dedicated to her late son Michael. But her ambition outstrips her talent, whereas her older brother works beautifully within his range.
If it wasn't that much more than a night at the office for them it was much, much more for some of us. Yes, they call it puppy love and it was all around in the excited arm-waving, snatched photos and the sense that the pair, for all the cheesy listening, takes us back to a better place.