Immortal dreams Why Putin and Xi are just the latest rulers to pursue an ever longer life

It was the stuff of Bond villains. Two ageing autocrats, their younger ally in tow, ambled down a red-carpeted ramp before a military parade in Beijing when an open microphone picked up a question that seemed to be on their minds: how long could they keep going - and, reading between the lines, might science allow them to rule for ever?

- Pjotr Sauer

With advances in technology, Russia's president, Vladimir Putin, assured his Chinese counterpart, Xi Jinping, via his translator, "human organs can be constantly transplanted, to the extent that people can get younger, perhaps even immortal". Xi replied: "By the end of this century, people may live to 150 years old."

Nearby, North Korea's leader, Kim Jong-un - three decades younger than the two 72-year-olds - appeared to take note with a smile. The hot-mic moment has stirred gossip about the leaders' shelf life, and inevitably, chatter about how far they'll push to keep the clock from running out. For now, there is no sign that any of them intends to loosen their grip on power. Each looks set to rule for as long as their bodies hold out, and none has offered a clear succession plan.