Jesse Karmazin’s Ambrosia Plasma clinic promised the fountain of youth, two litres of young plasma at a time.

For a fee, anyone could go to his treatment centre in the redwood forest outside Silicon Valley and receive an infusion. The results - according to Karmazin - were remarkable. Silicon Valley billionaires were rumoured to be queuing up for their young blood.

The problem was, the scientists whose work in mice he claimed to be bringing to the people disagreed with what he was doing, and he never backed up his claims with data. A journalist stepped in to investigate, and what she found was Silicon Valley hype without any substance.

In this series, technology reporter and psychologist Aleks Krotoski explores the frontiers of the extreme longevity pioneers. They've made their money in Silicon Valley. And with their technology solutions - PayPal, Facebook, cryptocurrencies - they've ushered in the world that we live in today, with all its unintended consequences. Some of them now want to solve the "problem" of aging, or even death, and they are making bigger strides than we may think.

Can they? Should they?

A Pillowfort production for BBC Radio 4

New episodes released Mondays. If you're in the UK, listen to the full series of Intrigue: The Immortals first on BBC Sounds: bbc.in/3WEQS5W