BBC wanted to "find the new David Attenborough" 20 years ago

Alastair Fothergill, who had just taken over as head of the BBC’s prestigious Natural History Unit in Bristol, tells Radio Times he thought it was a “stupid” idea.

“When I was made head of department back in 1992, John Birt – who as you remember was obsessed with objectives – set me one objective. He normally set all the heads of department ten objectives but he set me just one, and that was to find the new David Attenborough," Fothergill says.

"I never had the nerve to tell him, but I remember thinking, ‘That’s just about the most stupid thing I have ever been asked to do,’ because there never will be one,” he adds.

The special Radio Times Attenborough at 90 'birthday edition', available from Tuesday 3rd May

Fothergill, who is now director of Silverback Films, the makers of last year’s Attenborough-narrated epic The Hunt, says the veteran broadcaster is simply irreplaceable.

“It’s partly the history: the fact is he started at the beginning of natural history filmmaking and nobody else can start at the beginning. But it’s also the fact that he was an amazing filmmaker and producer in his own right.

"He has seen more of the natural world, not just of anyone in his generation, but anybody who has ever lived on our planet. His life has been perfectly timed. He started travelling in the early 1950s when the world was basically still pristine – the damage we’ve done has been done since then. So he’s not just seen more than anyone else but he’s seen more change than anybody who has ever lived.”

Fothergill, who describes Attenborough as both a modern day Darwin and “the best DG the BBC never had”, cites a moment when the BBC worried about their most famous broadcaster.

“Blue Planet was the first natural history landmark the BBC ever produced without David in vision. I remember literally right up to the night of transmission the BBC saying that this wouldn’t work," he says.

“They kept on saying, ‘You need David, you need David in vision', and it was a really, really big thing and they were genuinely worried. I was a bit worried. But the amazing thing is that everyone thought of it as an Attenborough series even though they never saw him in vision.”

Today Attenborough proves that Birt was a little premature in seeking his successor all those years ago. He’s already working on his next big series for the BBC – a sequel to the 2006 landmark series Planet Earth – which has seen him take to the skies in a hot air balloon over the Alps.

For the moment, though, he’s looking forward to celebrating his birthday next Sunday 8th May with a family lunch.

"I don't believe it actually, and all I can say is I am aware that I've been fantastically lucky," Attenborough says. "I have relatives and friends who are my age who can't remember anything, who can't move, and the fact that I can do both of those to some degree is just unbelievably fortunate."

Pick up the Radio Times David Attenborough 'birthday special' in shops and on the Apple Newsstand from Tuesday 3rd May

Attenborough at 90 – what's on TV?

Attenborough at 90, Sunday at 7pm on BBC1

Sir David shares some of his career highlights with interviewer and Desert Island Discs presenter Kirsty Young

Attenborough's Life that Glows, Monday at 9pm on BBC2

The broadcaster reveals "the amazing truth about living lights", from fireflies and glowworms to plankton and more

Attenborough's Passion Projects, BBC2 and iPlayer

Sir David introduces his favourite and most personal films for the BBC

Zoo Quest in Colour, BBC4

One of Attenborough's earliest films for the BBC, rediscovered for the first time in colour