Dame Joan Bakewell lives in an idyllic part of London's Primrose Hill. Her olive green painted Regency town house nestles in the corner, next to others decked out in delicate shades of pink, lemon and pistachio.

The centre of the square is a private garden, surrounded by railings and featuring a play area for toddlers plus inviting picnic spot for sipping wine on summer evenings. The differently-coloured facades and the friendliness of the garden soften the slightly lofty elegance of the place.

Quirky and colourful yet serious and elegant is a good way to describe Bakewell herself. Like so many faces we know from television, in person she seems familiar yet unknown, with all that vitality and intelligence oozing from every pore and the crisp, free-flowing manner of speech.

Up we go through the light-filled house: past an immaculate kitchen and a book-lined bathroom, into a gloriously sunny sitting room. Joan has a good eye for modern art - paintings and objects arrest the eye. Her coffee table harbours an eclectic mix of Harper's magazine, a book called Fathers, various arty brochures, a boxed set of The Wire and an Arctic Monkeys CD.

Forty years as a TV presenter at the BBC, starting with Late Night Line-up, and progressing through current affairs to fronting the Beeb's arts coverage later led to presenting moral issues series Heart of the Matter. Her many TV and radio projects included the controversial Taboo, which examined taste, decency and censorship.

She was a trailblazer, the Stockport girl who left grammar school to read Economics and History at Cambridge before a spell in advertising then a glittering career in broadcast journalism, at a time when the medium was largely populated by middle-aged men who sounded like (or were) Old Etonians. Her 2003 autobiography The Centre of the Bed deals in anecdotes from her very ordinary beginnings to her dazzling Swinging Sixties - juggling an "open" marriage, two children and home while also having a seven-year affair with playwright Harold Pinter and rising to prominence in the media. Her marriage to Michael Bakewell later broke down, and she and her second husband divorced a few years ago.

Now 75, and almost half a century since Frank Muir dubbed her "the thinking man's crumpet," Dame Joan Bakewell is still recognisably the beauty who (she says) took herself "very seriously, maybe too seriously" back then.

She says the label which became so beloved of tabloid editors hindered her career in current affairs for a while, but after whingeing about it for some time, it was other female journalists who told her to get over it. "They said 'shut-up Joan. As labels go, it's not a bad one.' So I did shut up."

In the distance Bakewell could easily pass for 50. Close-up, she looks about 60. Her brown eyes dance with vitality, her posture is straight and easy, her skin is porcelain and well cared-for, and the brown bob is subtly streaked with reddish blonde.

The understated grey trouser suit, dark top and beads are stylish yet safe... but she's zooming along on foxy red suede high-heels that sport a shiny black stripe up the heel. That splash of witty scarlet is everything.

When she was approaching her mid-70s, Joan decided to right a wrong done to her a long time ago, when a snooty English teacher said her school certificate in English didn't get a high enough mark to continue studying the subject in sixth form. "It really broke my heart. I did love reading and writing poetry, but she really slapped me down. Ever since then I have always hankered and yearned to write creatively. When TV began to close down for me, I began to think perhaps I could. Along the way I wrote some short stories and a couple of radio plays, and doing the autobiography showed me I could go the distance."

Almost 60 years later, the revenge that was so long in its gestation must be oh so sweet. Her first novel, All The Nice Girls, entwines the modern-day story of a mother contemplating giving a kidney to her adult daughter who is on dialysis with the wartime tale of giggly Manchester girls whose school joins the Ship Adoption Society, receiving visits from the captain and crew members of a merchant sea vessel involved in the Battle of the Atlantic throughout the Second World War. The strict school described is Bakewell's alma mater with a few embellishments. Cynthia, the very proper but stylish headmistress is fictitious, but the idea that this very well-behaved woman should fall in love in mid-life with a married sea captain is prompted by the speculation among the younger Bakewell and her teenage companions that their headmistress had a crush on the captain who came to visit bearing the gift of nylon stockings.

The bluestocking in the author loved the research process, visiting the Museum of the Western Advances in Liverpool, the Maritime Museum and Imperial War Museum, listening to first-hand accounts of life aboard merchant ships and various emergencies at sea.

"I used Liverpool in the book because it was the key dock for vessels crossing the Atlantic to fetch food and break the blockade of the German U-boats ... I came to feel that the Battle of the Atlantic has been rather neglected in the annals of war telling." For a woman who is associated with such a swinging and sexually liberated period in more recent history, Joan Bakewell is surprisingly (but refreshingly) reticent in her approach to sex scenes in the novel. But she's characteristically frank in her reasoning. "I don't think sex resides in the genitals, you know. Someone once said the greatest sex organ is the brain and imagination. I've always believed that. What is important is what grows between two people from the beginning. Josh and Cynthia do end up in bed together, but that to me is the natural progression.

"It's about their relationship, not about their limbs and body fluids, which I don't particularly enjoy reading about and don't think people can write very well." Bakewell tells a good yarn, but admits she had problems with over-plotting. The secondary story and its mysterious relationship to the wartime action is also broken up into sections, which makes the decision about organ donation appear to last an agonisingly long time. Why would she risk her character appearing unsympathetic by making her hesitate about giving the organ her daughter so badly needs? "I would be upset and anxious about having to make the decision myself," Bakewell admits.

Also, conversations with a transplant surgeon and patients gleaned the shock information that sometimes, when a good match is found between two family members, the potential donor asks the doctor not to divulge the match because they can't actually face surgery. JB attributes her own rude health, abundant energy and fitness to pilates classes, a couple of gym sessions a week, a handful of vitamins each morning - and work. "It keeps you thinking and tuned in. Being busy, moving about, getting involved, seeing people, it's all very important. There's a lot I still want to do ..."

She says she's waiting for the characters for a second novel to enter her head, although it's rumoured that she intends to use the period of the Cuban missile crisis as the setting. She happily talks about being older but doesn't groan about it. She just does it her way, and her way is a role model for anyone. You could marvel at how fantastic she is for 75, but she is marvellous for any age, and time spent in her company puts a spring in your step.

Another challenge she has taken on lately is that of the "Voice of the Elderly", a title she coined rather than "Tsarina". It's a role she's relishing, although when Harriet Harman first called and offered her the job she thought she was too busy, what with the book, still writing columns and making radio programmes.

"But then I figured I could be a good voice for older people because I'm known by the media and therefore accessible. But I said I would do it on my terms - not as a government job, but giving voice to what people think and want, answerable to my constituents. It has quickly become a crusade for me, and involves looking at all public policy in the light of how it will affect older people."

So what are the priorities?

"Oh, there are so many. I get many letters from people about all sorts of things, including their bladders and the terrible lack of public loos. Then there's housing and the pension crisis that's evolved ever since Mrs Thatcher unhooked pensions from the cost of living. Pensioners' groups are right to be so angry.

"There are a range of health and care issues, and end of life and assisted suicide. People write to me a lot about their fear of dying, and how they will be treated at that time." Bakewell has drawn up a living will about how she wants to be treated in various medical / care scenarios and her family are aware of her wishes.

One malaise, as Bakewell sees it, is that we are so terrified of old age. "It's a nasty place to go, and people don't want to think about it before they have to. But a wee bit of planning while still in middle age can make a big difference. Fitness and health in middle age help to govern what kind of old age you will have."

She'd like to see people negotiating their own retirement age with employers. "You might not keep the same job at the same rank, but there are negotiables including part-time work. When B&Q started employing people past the usual retirement age, there was 17 per cent less absenteeism among their staff. It makes sense on so many levels"

It's difficult to tell if Joan Bakewell quite sees herself as one of this group she's talking about, radiant and spry as she is. "I'm 75! Yes, I say 'we.' It's important to make that syntactical point: what we want, what we need.'' And does she feel anybody is listening? "Yes, I think so. Why else would they have asked me? I don't just go and schmooze, you know." The killer mixture of good sense, intelligence and charm must make her arguments irresistible.

As I walk away from the vivacious Joan in her olive-coloured house, passing the kids on tiny see-saws, I feel invigorated and certain she'd be first choice to bat on my side, whatever the cause or the game.

[ Sheena Hastings ]