BY the time Vanessa Collingridge is on her deathbed - a scene she can picture so readily that she invokes it twice this morning - she may have nothing to lament except a failure to pace herself. "Unfortunately," says Collingridge, "I achieved most of my life ambitions by the age of 33." That was three years ago. At 36, her CV is all over the place. A geographer, biographer, broadcaster, science writer, historian and former weathergirl, Collingridge has learned Latin for pleasure, lived among indigenous Central American tribes, survived a near-fatal brain virus, rowed across the Aegean in an ancient Greek trireme fighting ship, sailed the South Pacific route first charted by Captain James Cook, conducted field work on climate change in the Antarctic, and trained as a cosmonaut at Russia's Star City space centre.

Since becoming a mother recently, she has entered what she calls a "settling and consolidationperiod",buteventhis currently allows her to study for a belated PhD, consult on a forthcoming Australian documentary adaptation of her book about CaptainCook'svoyages,andprepare material for her new job as presenter of Radio 4's Making History programme, while taking her turn to host the local playgroup every Monday.

"Life is complicated for most people now, I think," she says. "Mine might be towards the more extreme end of this, but every freelancerIknow,particularlyevery woman, is juggling different contracts with family responsibilities. I'm lucky in that I don't need a lot of sleep, and I'm very good at focusing. Although just this week I was offered a TV series, and it was the first time I've ever had to say no' to something like that."

Collingridge and her family live in a farmhouse expensively restored from ruin on the shore of Castle Semple Loch near Lochwinnoch.HerhusbandAllanisat work. They met at Oxford University, where he was her rowing coach. "I hated him," she recalls. He is now head of marketing for the Royal Bank of Scotland group, and she envies him the budget at his disposal. Sons Archie, three, and 18-month-old Angus are at nursery. Baxter, their gigantic ridgeback hound,remainsonguardduty,which involves alternate rounds of sleeping and barking.

In the living room, there are plastic trains and crocodiles spilling out from underneath the piano. On top of it is a photo of CollingridgeinsideanIlyushin-76 parabolic aircraft, taken at a moment of weightlessness. While zero-gravity conditions of the kind experienced in such training planes are notoriously violent and nauseating, she looks as happy as a cosmonaut could be, her red curls floating outward from her head. "The cameraman was green, god bless him," says Collingridge. "And everyone else on board was having a really hard time. But you can see that I was having a ball." (Seconds later, gravity returned at double its normal earthly force, snappingherankleagainstthefloor. Collingridge had to complete her film for ITV's 1990s science show What Will They Think Of Next? - which she was producing and directing, as well as presenting - "with a fixed grin, while bouncing on one foot".) Over the past few weeks, Collingridge has been heard on the Radio Scotland series Buried Treasure, enthusing about the John Murray archive. The entire collected papers ofthateponymousLondonpublishing house - founded in 1768 by Scottish Royal MarinesofficerJohn(Mac)Murray,and which went on under his son and grandson to provide professional services and convivial afternoon drinks for almost every notable writer of the 18th and 19th centuries - were sold to the National Library of Scotland late last year, and the cataloguing is not yet complete, but this is already the second programme she has made on it for the BBC .

"Every week there are new discoveries," says Collingridge. "Almost on a daily basis. The beautiful thing is it's not just books and manuscripts, it's letters and notes, sales ledgers, scraps of paper. Jane Austen's first paycheck, with her name spelled incorrectly ... so she had to misspell her own name, essentially forge her own signature, to get the money."

An exhibition will follow in June, which is likely to foreground showpieces such as Byron's personal letters and Darwin's notes for Origin Of The Species, apparently recovered from storage in a drawer marked "underpants".

But what excites Collingridge are the wordsandpicturesoftheperiod'sexplorers. "Isabella Bird Bishop's travelogue diaries, she's always been a bit of a hero of mine ... and her photographs, which she developed on location, using water from the Yangtze river, or wherever ... Sir John Franklin's pocket notebook, which he was actually carrying on his search for the Northwest Passage ... All the marginalia, the scribblings, the little doodles, give you such aninsight.WhenDavidLivingstonewrites about being attacked by a lion, his writing is getting bigger and more exaggerated. You can see the emotion on the page."

The mere existence of the archive as a whole also seems to confirm the worldview that Collingridge developed through her study of geography, "the most fantastically general of sciences", which has taught her that everything is connected. This applies to most aspects of her own life and career, however random they may seem. Her PhD, for example, which is something that she promised herself after a paperwork mix-up at Newcastle University prevented her from doing one years ago ("I didn't want to be on mydeathbedsaying,IwishI'dgotmy PhD'") is about the historical geography of Antarctica. Lately she's been finding that manyofthereferencebooksinvolved mention either authors on John Murray's client list, or the publisher himself - "he effectivelystartedthewholeconceptof travel writing".

"I have been quite hard to pigeonhole in the past," says Collingridge. "I can see why someone might ask: Is she a scientist, an author, a presenter, or what?' Part of that is because of my magpie brain, and the fact I've always been a real have-a-go girl. But to me, I'm just trying not to be intellectually lazy, trying to keep a broad mind and see all the connections instead of splitting everything up into neat little compartments."

Collingridge grew up in Woking, Surrey, a towndullenoughtogenerateherearly interest in the exotic "messiness" of global exploration, particularly the culture clash visited on Latin America by the conquistadors. "They were my absolute passion," she says. "And old maps. Even in the Winnie The Pooh books, and Milly-Molly-Mandy, which youwouldopenuptoseethesemaps inside the covers, of Hundred Acre Wood or wherever. I've been a cartography geek ever since, and my main personal research interest has been the secret language of maps, the hidden information they contain, the idea that they're windows into the mind of historical cultures."

Neither of her parents had been to university. HerScottish-born mother,shesays,was tacitlydeniedaccessto thisbecauseofher council-estatebackground, while her half-Irish father dropped out of school to enlist in the air force during the second world war. "But they were very bright people, passionate about learning." Collingridge is the youngest of five children, four of whom now have some form of Oxbridge degree. She elected to study geography at Hertford College Oxford for two reasons - the rowing (she is exceptionally fit), and the fact that they did thebestexpeditions.Asa"rad-fem"productofcomprehensive school, her experienceatuniversityvalidatedcertainprejudices."I found the institution smug, self-serving, and totally patriarchal. I had quite a hellish time in many ways. Saying that, after the schoolsI'dbeento,whereitwasn'tcooltobeenthusiasticabout learning, it was also incredibly liberating to suddenly be comfortable with my intellectual excitement."

In her second year, she contracted viral encephalitis, which caused brain-swelling so severe that it wasn't certain whether she would live, let alone finish her studies. "I learned a bit of humility from that. A bit of calm, a bit of zen. I'm quite hyper now, but at 18 I was 10 times worse. With the books I've written Captain Cook in 2002 and Boudica in 2005, I think I'm still asking myself if my brain is able to cope with serious academic work after the encephalitis." During her illness, she would consider it an achievement if she could even read one paragraph of a book about the Zapotec people of Mexico. When she recovered, she went to live with them for the purposes of her undergraduate thesis, which refuted the beliefof"arrogant,sexist,maleWestern scientists" that Zapotec women could not effectively regulate their fertility by use oflocalplant-basedinfusions.Her conclusions were unpopular - today she remembers the exact words of her tutor: "Ms Collingridge, I really don't think thatpost-coitalvaginaldouchesexist within the realms of geography" - but earned her a first-class degree. Not long afterwards, when her PhD fell through, she was putting her researchlibraryexperiencetouseasa question-checker for TV gameshows Wheel Of Fortune and Win Lose Or Draw.

"It was brilliant, because it was fast and furious. Every minute of stoppage time cost thousands, so you had to be rigorous in your research. But I knew I wasn't a light entertainment person." Through a series of contacts and coincidences - Collingridge does her best to provide a chronological precis, frequently using the words "la la la" in the same way that other people might say "etcetera" or "and so on" - she was offeredajobasTVweathergirlbyBBC Scotland,whodidn'tappreciatehow over-qualified she was until she was hired.

"I got away with murder. The day producer would cast his eyes over the script, but basically I had total control over two or three minutes of airtime. So I had warm wet tongues licking the coast'. Or I had alliteration days where it was going to be dreich and drookit in Drumnadrochit'. I only did it for 14 months, and that was 13 years ago. I was looking for a slightly bigger challenge. But I'm still being constantly referred to as a former weathergirl'."

From there, "la la la", Collingridge found herself commissioned to make increasingly regular, varied and specialised contributions to programmes on every one of the UK's terrestrial TV networks. She has lived in Scotland since 1989, but didn't tell London producers that, paying her own air fares as a commuter, until a new channel called Five picked up the tab when they made her their science correspondent. By the time she was headhunted away to report for ITV's Tonight With Trevor McDonald, she was working 50 days straight, with one-day breaks. On a walking holiday in New Zealand around 2000, she said to her husband: "This is totally unsustainable." "He said: What is?" She said: "This life." So she quit, to do the "onething"shehadalwayswantedto. "Write books. Tell stories. I didn't want to be on my deathbed wishing I had done it ... "

WithCollingridge, however,thereis always one, or two, orfivemore "things".Ifsheis primarily an author now, she is also still a broadcaster, a student, a lecturer, and climatechangescientist,whotooksix months off in 2003 to join the Royal Geographic Society's New Scotia expedition to Antarctica. ("Humans have definitely left their fingerprint. The difficulty is that we don't understand how climate works, never mind the impact that we've had on it. But you go on best evidence, and you do what you can.") Given that there's still a whole world out there, and so much work to do in it, I am a little surprised that she has had two children since that expedition. To put it another way, I'm still trying to connect the toys on the floor to the trainee cosmonaut in the photograph, and I'm wondering if this has been a problem for Collingridge herself.

"Well," she says, "I didn't have kids until I'd been on all seven continents. Two weeks is the longest I've been away from them, and I wouldn't want to go any longer than that, because by the end of two weeks you can see it's having an effect. Some things are more important than your career. But Al is a very hands-on dad. He has to be. He always wanted to have children, where I was always, No, I won't, I can't, la la la'. And when we did have Archie, I said, I'm sorry, he's your child as well, and I have to keep working'. I'm not the kind of person who is happy to do just one thing, and that includes being a wife and mother."

Buried Treasure: The John Murray Archive is on Radio Scotland, today,11.05am.

Making History is on BBC Radio 4, Tuesdays, 3pm