Revered nature broadcaster Sir David Attenborough is to undergo emergency heart surgery in London on Tuesday (04Jun). The 87-year-old Brit was advised to schedule the procedure after his cardiologist determined him to be in urgent need of a pacemaker. Attenborough has been forced to cancel a planned speaking tour of Australia to undergo the operation. The tour, entitled Sir David Attenborough - A Life on Earth, was due to start next Tuesday (11Jun13) in Brisbane. A representative for the organisers, Lateral Events, says in a statement, "Sir David Attenborough is to undergo surgery in London today (04Jun13) following advice from his cardiologist that he is in urgent need of a pacemaker. 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."