Is $3bn really enough to cure all the disease in the world? I mean, it’s not nothing: it could buy you a cluster of swanky mansions on the Cote D’Azur, for example, or a couple of Roman Abramovitch’s mega-yachts. But it wouldn’t touch the sides of this year’s £114.6bn NHS budget – and even that, we are told, is barely enough to keep the health service in surgical stockings.

One doesn’t like to sound ungrateful. It’s lovely that Mark Zuckerberg and his wife, Priscilla Chan, want to save the human race. But still, their promise to find ways to “cure, prevent or manage all disease” by the end of the century does raise a few niggling doubts.

The Facebook founder and his wife, a paediatrician, made their announcement in San Francisco this week.

It was a standard silicon valley press conference: two mega-rich nerds in T-shirts pacing the stage, talking into tiny headsets, in front of an audience of whooping, fist-pumping worshippers.

One almost sensed a touch of anti-climax when it became clear they were not unveiling a new Facebook “like” button, but a complex, long-term philanthropic project to save all humanity.