The ‘irreplaceable’ nature presenter has again raised the idea of stepping away from the camera. But when he does finally stop, who might step in?

David Attenborough has again raised the idea of his retirement, should his work start to become “substandard”. In 2014, Wendy Darke, then head of the BBC Natural History Unit, stated that she could not see “one person” ever taking over from Attenborough, whom she described as “a legend and an irreplaceable one-off. He is a storyteller without match, so we would never attempt to fill his shoes.” His various roles, she suggested, were likely to be distributed among a number of presenters, who would reflect the “need to continue to innovate and diversify”. Some of these hosts, she hinted, might be drawn from different academic disciplines. Tantalisingly, though, Darke has since left her post, replaced by Julian Hector, and it is not clear whether the idea still applies.

David Attenborough: I'll retire if my work becomes substandard Read more

If Hector is sensible, it will. Attenborough – musing to Radio Times this week about how long his career might continue – expressed separate concerns about restricted mobility preventing filming or vocal deterioration affecting his voiceovers. Such a brand is irreplaceable, especially in a TV era properly questioning monolithic opinion: Lord Kenneth Clark, solo host of the 1969 BBC art overview Civilisation, will be replaced in this year’s remake, Civilisations, by a trio: Mary Beard, David Olusoga and Simon Schama. If a post-Attenborough portfolio were to be similarly split, here are the obvious – and less obvious – contenders.

Chris Packham

Facebook Twitter Pinterest Chris Packham Photograph: Richard Ansett/BBC

The non-alphabetical list of a dozen key presenters on the BBC Natural History site gives Packham second position after Attenborough, suggesting his status as vice-president in any straight succession race. A three-decade TV career from The Really Wild Show to Earth Live certainly gives him the presenting credentials to take over the frequent-flyer frontman part of the Attenborough portfolio. A recent thoughtful autobiographical film, Chris Packham: Asperger’s and Me, revealed an interesting hinterland.

Liz Bonnin

Facebook Twitter Pinterest Liz Bonnin

Liz Bonnin: 'I'm still a nerd, just a different type of a nerd' Read more

Born in Paris to Trinidadian and French-Martiniquan parents, then brought up and educated in Ireland, Bonnin has a strikingly broad background and an equally diverse TV CV. After starting on Top of the Pops and RI:SE, she put her degree in biochemistry and masters in wild animal biography to use in shows such as Bang Goes the Theory and Super Smart Animals. Last year’s BBC One hits Galapagos and Wild Alaska Live saw her confidently conquer the crucial Attenborough skills of getting close to creatures and rhapsodising over geographic spectacle.

Kevin Fong

Facebook Twitter Pinterest Dr Kevin Fong Photograph: Graeme Robertson/The Guardian

The presenter of several editions of BBC2’s Horizon and the ITV show It’s Not Rocket Science! is another converted scientist. As a consultant anaesthetist for London’s UCL hospitals, Fong is unlikely to be available for long, remote shoots but, as a clever populariser, could be an attractive part of a post-Attenborough team approach.

Lucy Cooke

Facebook Twitter Pinterest Lucy Cooke

Inspired to study zoology by Attenborough’s landmark 1979 series Life on Earth – and taught at Oxford by the likes of Professor Richard Dawkins – Cooke has a useful double inheritance from the highest-profile science broadcasters of the times. Her TV work – including Amazing Animal Births on ITV and Nature’s Miracle Orphans for BBC One – is more sentimentally anthropomorphic than Attenborough’s approach, but she seems a likely part of any post-Attenborough strategy.

Brian Cox

Facebook Twitter Pinterest Professor Brian Cox

Prof Brian Cox: ‘Being anti-expert – that’s the way back to the cave’ Read more

It has been a recent BBC habit to move expert presenters from their core specialism to another, with Lucy Worsley and Simon Schama shifting from history to arts. BBC managers have intermittently hinted at a similar solution to filling the post-Attenborough hole. If so, the charismatic, accessible Lancastrian astrophysicist would be a good bet to shift his televisual gaze from the stars and planets to the Earth and sea beneath.

Richard Mabey

Facebook Twitter Pinterest Richard Mabey Photograph: Ireland/Rex/Shutterstock

As a concession to his age and increasing frailty, some later Attenborough series, such as Blue Planet, involve him as writer-narrator rather than reporter. If this line of work were ever to continue without him – and Blue Planet is currently one of the most bankable franchises in TV – it seems most likely that a BBC selection committee would opt for Stephen Fry or Michael Palin. However, the 76-year-old Mabey would make a fascinating wildcard; he is one of our greatest nature writers, through dozens of books including Flora Britannica and Food for Free. Probably only he could contribute commentaries to match the gravitas and knowledge of Attenborough’s.

Prince Charles

Facebook Twitter Pinterest Prince Charles Photograph: Toby Melville/AFP/Getty

A long shot, and likely to divide the audience. But, if the Queen carries on long past the retirement of her fellow nonagenarian Attenborough, an increasingly desperate Charles may eye a holding job as successor to another notable advocate for environmentalism.