Naturalist David Attenborough (87) is having a pacemaker fitted as a matter of urgency and has been forced to postpone his Australian tour.
A statement from the tour promoters, Lateral Event Management, said: "Sir David Attenborough is to undergo surgery in London today [Tuesday] following advice from his cardiologist that he is in urgent need of a pacemaker."
The statement continued: "It is with regret, therefore, that Lateral Events CEO Simon Baggs announced that the forthcoming sell-out tour of Australia, scheduled to begin in Brisbane next week, has been cancelled.
"Sir David expressed his extreme disappointment as he said he was very much looking forward to coming back to Australia and he hopes to reschedule his tour in the near future."
