The scuba diver: Margaret Scott, 80

Scott is proud of her scuba-diving hobby. So on her 72nd birthday, in keeping with her tradition of "doing something special", she dived to a depth of 72 feet and, once she had got down there, the odd carp swimming about her weighted ankles, did a spot of knitting. Somebody had told her shortly before that she shouldn't be diving at her age - she should be doing sensible things. "And that clicked," she says. "It was a giggle."

She is, to say the least, single-minded, always travelling alone, preferring a tent to a hotel, "not tied to friends", and unaccompanied by her husband, Eric Woodward ("I didn't take his name when we married. That was 1954."). If her children need her, she says, they ring her. Now, 10 years after taking up the sport, she has completed 260 dives. "Can you imagine flying in the air as a bird?" she says. "It's that sort of thing, only in water."

Scott first became interested 10 years ago when she was on the sports council in her local borough of Sandwell in the West Midlands. She was already swimming every day, and when she began to take the tests she soon showed up the poor chap in his 30s going through the ropes with her. At the end she passed; he failed, and was never seen again. There was, she says, "slight surprise" when she got through. "'Good gracious me,' the instructor said. 'I never thought you'd do it.'"

It was the start of a passion that has taken her not just to the diving pool at Leicester once a fortnight, but all over the world, most enjoyably to the Maldives (for the exotic fish) and to Scapa Flow, where her father served in the navy - an experience he told her about when she was a child. "It was not only history," she says, to dive there, "It was my life."

But she never gets nervous. "No, no, no, no." And she won't hear herself described as brave. "Committed," she says. "And you've got to be prepared for realising that you can't move as fast as younger people do, and it's no good trying. You've got to realise your weaknesses."

So how much longer will she keep diving? "I know there'll come a time when I can't do it any more," she says, "and I avoid thinking about it. So I'm hoping I'm going to be doing what I'm doing now, and then death. I don't fancy the in-between bit."
Paula Cocozza

The journalist: Rose Hacker, 100

Last year, at the age of 100 and after being a politician, writer, artist, sex therapist and peace activist, Hacker became a journalist. She was at the anniversary of the bombing of Hiroshima in Tavistock Square in London when a local newspaper reporter saw her give a speech and suggested she write a regular column. Called "She's 100 so she should know a thing or two", it runs in the Camden New Journal, a north London newspaper, every fortnight. She has written about issues including homelessness, the wealth gap, the divisiveness of religious education, greed and property ownership. "I've got so much I have to say. I look at my great-granddaughter who is three years old and think, what sort of world has she been brought into? I just can't bear it."

Every couple of weeks, a reporter comes to her room at the retirement home in north London where she lives and types away at a laptop while Hacker talks, surrounded by books on politics and art and photographs of her family. "Then he shows me on the screen in a big font so I can read it," she says. "It's very exciting. I can do anything - they don't tell me what to write.

"It has given me a new lease of life. I was dying. I had my 100th birthday and everybody gave me parties; I had a wonderful time. Then I collapsed. I was unconscious; I had everything wrong with me. Now, in my second century, I'm like a baby, I've started all over again. I had to learn to walk again, come out of nappies."

It's not often that you meet 100-year-olds, but it seems unlikely that many are as lively as Hacker. She is partially deaf and blind but she walks unaided and her mind is crammed with information. She is funny, too. She's wearing glamorous, big silver earrings that dangle furiously when she leans forward in her chair to make a point - and she has an opinion on everything.

Hacker was born in east London to Jewish parents. Her father, an immigrant from Poland, ran a tailoring business and Hacker became one of his clothes designers. Having always been interested in politics, she joined the Labour party and got married - to Mark, an accountant (he died in 1982, after 52 years of marriage). She gave up being a designer when she had children - two sons - but later joined the Marriage Guidance Council and became one of Britain's first sex therapists. She wrote several books, including one about sex for teenagers. "Nobody talked about sex in those days," she says. "These days, it's all everyone seems to talk about".

"It would be so easy for me to sit in this chair, listen to music and do nothing," she says. "I can understand people my age who just give up." So why doesn't she? "Because of the state of the world. I think it's very important that people should listen to people like me - and we're being totally ignored." Does that make her angry? "Yes. But I'm furious about everything." Not least what Hacker, a lifelong socialist, sees as the betrayal by New Labour. "I wrote to Blair and said if you go to war in Iraq, after 80 years of hard work I will resign. The same day I got a certificate that makes me an honorary lifetime member of Highgate Labour party, so I'm not sure I can." Did she ever think the future would be this bad? "No, I thought we would have a wonderful future. We'd built a welfare state and it worked. We had a health service. We built schools. But the monsters have taken over the world."
Emine Saner

The keep-fit fanatic: Seona Ross, 90

Ross is 90 and has just made her first exercise video. "I enjoyed it thoroughly," she says. "It was fun, a real challenge. I had three members of the exercise class I run working with me to show that older people can do it. I had thought about doing a video before when I was younger but never did, so when Help the Aged asked me, I agreed without even thinking about it. I hadn't seen any [other videos] I thought were suitable for older people." For the elderly, exercise is, she says, "absolutely essential. The main thing about the work I do with senior citizens is it is keeping them in their own homes. I'm saving the NHS and the government a hell of a lot of money. I've had people come to me who decide they don't need to take all the pills they had been taking - they're not going into care homes."

The video and DVD, Step to the Future, contains 40 minutes of exercises for older people. "Exercise is vital in having the right attitude to life. All those endorphins are good for you. The video shows that older people can exercise and enjoy it, but we focus a lot on how to do it safely." In her classes, Ross, a music fan, relies on good tunes to keep her members moving. What did she choose for her video? "The music was dead boring, to be honest," she says and laughs. So what does she choose for her class? "All sorts, but very little of your modern music - as far as I'm concerned, that's not music at all. All that repetitiveness." She makes an exasperated noise. Ross likes Latin American music and old showtunes.

Ross, who has three children, six grandchildren and six great-grandchildren and lives in Wiltshire, decided she wanted to become an exercise instructor when she was 14 and saw a demonstration by the Women's League of Health and Beauty in Glasgow, the institution founded by Mary Bagot Stack to introduce exercise to all women. "My parents thought I was mad and said I had to finish school."

Just before she turned 17, she moved to London and attended Stack's school to train instructors at a time when women were expected to be able to dance, but not do these strange stretches and jump around in shorts and vests. "We were pioneers," says Ross. "We would do demonstrations in Hyde Park and great crowds would come. They must have thought we were mad but we were treated like pop stars."

Now, in her 10th decade, she says it is exercise that has kept her young. "I still go out and enjoy myself and see my friends. I'm just as fit and frisky as I was when I was 70." Step to the Future is available on DVD and video (£12) from www.helptheaged.org.uk/homeshopping or 0870 770 0441
Emine Saner

The violinist: Leonard Hemming, 83

Many adults believe it's too late to start learning an instrument, but that didn't stop Hemming, from Hertfordshire, taking up the violin at the age of 75. An avid music lover, Hemming had sung in the London Philharmonic Choir for many years. When his voice began to deteriorate, he felt bereft. "Music has always been essential to me," he says. But then a friend's abandoned violin provided him with the perfect opportunity to reintroduce music to his life.

Taking lessons and practising daily, Hemming, who's now 83, today plays in the East London Late Starters' Orchestra. The ELLSO gives people of all abilities the chance to participate, particularly those who missed out on music in earlier life.

Hemming thrives on the social life and performances: "You can play until you drop. I can't claim it's easy but it's fun from the word go."
Nadia Saint

The dancer: Vera Comben, 78

"I was into dancing as a teenager," says Comben, from Leeds, before adding hastily, "just ballroom dancing, nothing exotic. But then I married and had children." Her husband, who worked his way up from a bus driver to chief cashier on the Leeds Metro, was not much of a one for the dancefloor. "I did mention to my husband that he might like to try dancing," says Comben, "and he said, 'I've more to do than push you around t'floor all night.' That was the end of that discussion. And I was married 54 years."

So when her husband died last April, Comben decided that it was not too late to get started on her long-lost hobby. "I decided that I needed to do things for me," she says. After trying to join a ballroom group, which had to be cancelled due to lack of interest, Comben signed up for dance and drama classes on the Heydays programme for the over-55s at the West Yorkshire Playhouse. "The first session was line-dancing, which I found too much," she says. "I did it for about a month, and then I dropped out of that. I just ran out of puff."

Undeterred, Comben signed up for contemporary dance instead. "It is a version of ballet," she explains, "but not so energetic. The first session was on Wednesday morning. We did getting up on to your toes and down to your feet, as well as some massage, and obviously dancing around the room. It's not too energetic at this stage, but I've got a feeling it will get more so. I'm thoroughly enjoying it."
Leo Benedictus

The skydiver: Doreen Nichol, 70

Falling through the sky with only a bit of fabric for support is something few of us would consider lightly, what ever our age. But last year, at 69, Nichol took the plunge and skydived to raise more than £600 for Help the Aged. She had never done anything so extreme before, but is amusingly nonchalant about her experience. "Heights have never bothered me," she says.

When her husband died almost four years ago, Nichol, who lives in Sunderland, found herself alone and bored. "I just sort of sat around," she says. Working in her local charity shop, where she noticed the skydiving advertisement, improved her life and inspired her to raise money. Since her aeroplane jump, Nichol has enjoyed a variety of new experiences, from flying in a helicopter to taking a luxury cruise.

While she has no immediate plans to repeat her skydive, Nichol is adamant that she would do it again. "I thoroughly enjoyed it," she says, despite a few pre-jump jitters. "You do get nervous. Especially at my age!" But she believes that age should not always be seen as an obstacle. "Young and old - we're all alike. You're never too old to do things if you want to."
Nadia Saint

The model: Hazel White, 75

White woke up one morning, five years ago, and decided she wanted to be a model. "I can remember exactly the day that it happened," says White, 75, from Hitchin in Hertfordshire. "I was looking in the mirror upstairs in the bedroom. Someone had given me a card which said 'Ugly's' on it, and I thought, 'Yes, that's me.'" Ugly's is what's known in the industry as a character model agency, specialising in "interesting faces", rather than size-zero blondes preferred by the other big agencies.

So she gave Ugly's a call - and has been modelling ever since, spending her days attending castings, hanging out with photographers and appearing in magazines. She is very good at crumpling her face, she says, "which seems to make people laugh."

If someone is looking for an archetypal granny, it is White who gets the call. She describes her look as "very white hair", "not plump" and a petite 5ft 4½in. "That extra half is very important."

So what makes a 70-year-old woman go into an industry where anyone over the age of 30 is often considered past it? "I wanted to act when I was younger. I can remember telling my father, who was then a prison officer, and he said, 'No, my darling, you get yourself a proper job', so I went and joined the bank and became an ordinary person."

And then, several decades later, that ordinary person remembered her desire to make a splash and decided to give modelling a go. "I went to castings first of all. They are horrible - you go into the room with lots of other old ladies with white hair, all sitting there, some of them chatting and some of them not. It's quite offputting - I don't like it at all. I usually pretend I've gone deaf."

Has she ever been tempted to smooth out her wrinkles? "No, I don't think I would. I've thought about it sometimes, especially when you're feeling a bit low and you look in the mirror and you think, 'Eugh!', but it's my face. I've got lots of lines, but that is something that is an asset really."
Hannah Pool

The student: Bernard Herzberg, 98

Herzberg was 81 when he did his first degree, and is now just months away from getting his MA in African economics and literature at the School of Oriental and African Studies (Soas) in London. His final paper, an essay on the inevitability of military rule in Africa after decolonisation, was handed in four months ahead of the deadline.

"This is the second time I have written this essay," says Herzberg, who lives in East Finchley. "The first time the lecturer did not agree with the way I wrote it, so I had to redo it." This time the 98-year-old is confident that he will pass. But whether he does or not hardly seems to matter: his wife died last month, and studying is now a way for him to keep himself occupied. "I didn't want to sit at home doing nothing, especially now that I am alone," he says.

At Soas he has made many friends among his fellow students and lecturers, all of whom are a lot younger than him. "Do they treat me well? Oh, yes, very much so."

As a Jew growing up in 1930s Germany, Herzberg was denied the chance of a university education. In his early 20s he emigrated to South Africa, where he lived for half a century before moving to London in 1985. Married with two children, he didn't get round to university until after he had retired from the chemical industry in his early 80s. But this latest MA will join a long list of educational achievements, including another MA in refugee studies gained in 2005, and a degree in German and German literature before that.

Whatever the outcome in May, Herzberg is satisfied with his accomplishments. "Whether I get the third degree or not is immaterial," he said. "I have lived a good life."
Mildred Amadiegwu