A few weeks before I’m scheduled to meet Bryan Johnson, his handler sends instructions: please keep the address for his Los Angeles mansion discreet. It’s a shoes-off household so maybe wear socks because the concrete floors are cold. And “FYI,” she adds, “Bryan does not go in the sun.”

It’s a shame, because the southern California sky is a beautiful blue as I pull up to the angular grey warehouse where Johnson lives, vampirically, and from which he runs his biohacking empire. Johnson, who sold his payments company, Braintree, to PayPal for $800mn in 2013, has become the most prolific Silicon Valley techie in the longevity and anti-ageing field. He’s done this by fusing the sincerity, self-confidence and data fanaticism that builds successful start-ups with a knack for creating viral, sometimes bizarre, wellness content.

Having recently embarked on a performative one-man quest to live for ever, Johnson is experiencing a moment in an even bigger spotlight, as the subject of a Netflix documentary. The buzz of self-belief is palpable as he shakes my hand and explains, soft-spoken but upbeat, that he’s come straight from his hyperbaric chamber, a tank worth about $120,000 in which you can breathe pure oxygen.