In the absence of a control Joan, we can't be certain that the face of the comedian Joan Rivers, after countless procedures, amounts to one of the most effective warnings imaginable against cosmetic surgery.
Maybe if we could see how her face would have looked, naturally, at the age of 78, middle-aged women would contemplate Rivers' soaring eyebrows, cat's eyes and those stiff planes that prevent a pair of inflated cheeks collapsing on to a mouth that is not so much trout as platypus, and conclude that, yes, hers is definitely an improvement on the conventional package of furrows, sagging jowls and turkey neck - a masterpiece of cosmetic surgery.
Hasn't another brilliant American, Nora Ephron, said that one of her biggest regrets "is that I didn't spend my youth staring lovingly at my neck. It never crossed my mind to be grateful for it". And yet: Joan Rivers? Even with a smooth neck? Now she has been kind enough to film the latest adjustments for a TV reality show, viewers can judge for themselves.
While the industry worries about the rights and wrongs of advertising eternal youth, Rivers demonstrates how it might look.
In fact, in the absence of long-term studies on cosmetic surgery outcomes, its potential victims owe Rivers, along with her fellow guinea pigs, a debt of gratitude. Like the ring-necked members of the Karen tribe when trotted out for tourists, the women must know their appearance will invite as much horror as fascination, but their sacrifice helps save others from a similar fate. Were it not for Rivers' permanently agonised mouth, British TV presenter Anne Robinson's startled stare, the remains of Priscilla Presley's face and a host of fluctuating celebrity bosoms, how many more women would believe the doctors' assurances that their interventions really can, as the well-known Harley Medical Group in London puts it, "enhance the appearance of the face, both as an anti-ageing technique and as a way to address issues people may have with the way they look"?