Sir David Attenborough made a huge personal sacrifice to film his latest BBC documentary, producers have confirmed. The nature expert and all-round national treasure gave up marking a big milestone to be on set to film Asia, his latest series taking viewers on a tour of the world’s largest continent. Now bosses have explained to Yahoo how David missed out on celebrating his 98th birthday to film the nature programme.

Executive producer Roger Webb explained: “David is irreplaceable. "He's a unique human being. We've got a fantastic cast of up and coming — and some very established — presenters, but they have their own style, and they do their own thing.

He's a unique character and long may we continue to work with the great man and, for as long as he wants to work, we will work with him." He explained: “It's just brilliant to be able to work with David. We were working with David on his 98th birthday.

The respect for that man is off the scale...

The fact he's still going, still setting an incredible bar for what he does and how he does it. At 98 years old, I just take my hat off to him." David not only films his voiceovers for the programmes, but actually helps to write the final scripts that will be used to provide his “own take on things”.

It took four years in total to film Asia, though Attenborough didn’t travel to the continent for filming, but rather stayed in the UK. It comes a decade after BBC bosses feared for David’s health while he filmed on locati.