Anyone travelling in the crush of London Underground's District line last week could have seen a tiny woman with dark brown eyes, a sharp nose and witty face, talking in heavily accented English with a younger man. Most wouldn't have known that this was one the city's most admired prima ballerinas, Daria Klimentová, with her dancing partner Vadim Muntagirov, on their way back from rehearsals in east London to prepare for a farewell performance at the Albert Hall.

The forthcoming English National Ballet production of Romeo and Juliet will conclude the ballerina's 25-year career and end one of dance's most acclaimed double acts. Klimentová, 43 this month, has decided to give up dancing not just for her loyal audiences in London, the city that after her native Prague has become a second home, but to give up dancing professionally for ever.

"Of course it is very emotional and scary. It is a huge moment," Klimentová told the Observer this weekend as she looked back at a life in dance that began at the heart of the communist system of elite training in Czechoslavakia and eventually took her around the world. "Vadim is more fine about it than me, I think," she said. "He is 19 years younger and knew from the beginning that he would be dancing with someone else one day. It is harder for me. For me it is completely over."

The ballerina has plans to teach and perhaps to return to Prague to run a ballet company, but fears for the future of classical ballet. Audiences were dwindling and some choreographers mistakenly taking desperate measures – jazzing up productions – to draw in the crowds, she said.

"Classical ballet is already getting smaller and smaller. I hope that it is not going to disappear. But what I see around me is a lot of choreographers who are destroying the classics. I wish that instead of doing Sleeping Beauty in some crazy new way, they would just go and invent their own full-length ballet story."

Klimentová exempts Matthew Bourne's acclaimed and innovative company from her criticism. It has set out to challenge the classics. It is the national ballet companies that annoy her when they attempt to copy Bourne's tricks, rather than concentrating on keeping the traditions alive. "They destroy the magic when they change them, say by putting Juliet in shorts. Maybe I am old-fashioned. I know you have to go forward. But there is a reason why these ballets are called classic. They are magical."

Fresh generations should be able to see a classic Cinderella or Sleeping Beauty, she argues. "Why destroy a masterpiece? That drives me mad."

If Klimentová is sometimes recognised on the tube it is because of her appearance three years ago in the BBC4 television documentary Agony & Ecstasy, where she gained viewers' sympathy for her apparent rough treatment at the hands of former artistic director Derek Deane.

"I watched the show for 30 minutes and I thought, 'Oh!' But it's OK now. I have known Derek Deane for 12 years and he is tough with everyone. It doesn't matter if you are the star or the last person in the corps de ballet. And I also realised that all the comments shown weren't directed at me. The TV people cut it to make more of a drama."

This summer will see an abrupt change to the strict regimen of life since her Prague childhood. "I will have to exercise just to feel good, because I have scoliosis [curvature of the spine], which is nothing to do with the dancing. And anyway it is not good to suddenly stop. It would be a shock for the body and for the mind, so I will join a fitness centre and take up yoga."

She was, she said, really looking forward to taking charge of her own daily timetable. "One of the reasons why I am stopping is I have had enough of people telling me to stand over there in the corner and smile. And when you get younger directors coming in, you know it is time to go."

Her daughter Sabina has no ambitions to dance, which pleases Klimentová because, as she bluntly puts it: "I don't think she is talented so she would suffer." Yet she would not discourage others. "It is an amazing life if you make it as a ballerina. If you stay in the corps de ballet, most of the time it's not amazing. Although the corps can be good too for some people, unfortunately they all want to be Juliet."

There is no chance Klimentová will take it easy for long. On Thursday she finished her teacher training exams at the Royal Ballet School and she is weighing up an appealing offer to go back to Prague as the artistic director of the Czech National Ballet.

Her attitude to food would not be changing, she said. "I am not on a diet and I was never on a diet, so I will eat absolutely the same like I always did. I am just naturally looking like this, ill, all my life!"

She loved the sausages, cheeses and bread of her homeland, she said.

Her petite figure and flexibility as a girl marked her out for training as a potential Olympic gymnast in Prague and she only switched to ballet on advice she would enjoy a longer career. At the time she shared a flat with her mother, her late father and a brother, later killed in a road accident, and she had never seen a ballet production.

"We could only buy bananas in the winter at Christmas and we didn't have toilet paper. But I wasn't unhappy. I didn't know anything else. I didn't want 10 watches or a Burberry handbag."

As the Soviet bloc faltered in 1989, Klimentová won a competition to dance in South Africa and later left reluctantly, planning to come back after making some money and learning English. "Things were easing up for travel when I was leaving school. And I had an offer to join the Scottish Ballet. I feel sorry for ballerinas who were 10 or 15 years older than me. They couldn't travel, or only to eastern Europe and Russia. I was very lucky. I have been very lucky all my life."

The world she left in Prague disappeared, along with half of her small family, but Klimentová still carried it with her, she said, touching her heart. "It is here all the time. We Czech people can never forget."

All the same, the prospect of returning to work in Prague, where she gave a farewell gala performance 10 days ago, worries her. "I am very sad there is so much corruption. There is a big mess in politics. One day there is one minister of culture, the next day he is not there. It is crazy." She acknowledges though that under communism the same thing went on. "There was corruption under communism, we just didn't know about it."

Popular ballet mythology has it that Klimentová extended her career because of Muntagirov, but she said she had not been ready to retire until now. "I was looking for a partner I could get on with and Vadim was a complete accident. He was supposed to have a different partner, who went off. So he didn't have anyone and I was the only one available."

When the two take to the stage for the last time as Romeo and Juliet on 22 June, they will be saying goodbye to a working union that has seen them compared to Margot Fonteyn and Rudolf Nureyev. And like many ballerinas, including Fonteyn, Klimentová feels she has become a better Juliet with age. "You use your own life experience. I play it much better now I am older. I didn't know about death. Now I have experienced it myself. You have to grow into Juliet."

Her transition into teacher is only just beginning, the dancer suspects. "Yesterday I was happy when I passed my last exam and then suddenly I thought, 'I am teacher now.' How can I be a teacher? I am a dancer. I will have the paper, I am qualified, but I am not quite ready. It is hard."

She does believe, however, that the combination of her Soviet bloc training and the Royal Ballet School methods will be useful: "It would be a shame to keep all those years of experience for myself when I could help some young talented dancers."

Physical aptitude, she said, was the key thing for a dance student. Without loose hips and mobility they would never thrive in ballet. Musicality and acting, in contrast, could be learned with good teaching. "I will be learning as a teacher all my life, but the key thing must be to understand the students and not to be a bully like quite a lot you see around. I want them to want to work hard though. You cannot be too nice."

For now Klimentová's greatest apprehension is not her last London performance but the party that awaits her afterwards. "I like to be on my own. I don't get lonely and I always want to go home. I should be nervous for the show, but I am actually nervous about the party the company is organising!"

What is odd, the ballerina admits, is that this shy woman has loved the adoration of her London audience. "It is amazing at the curtain, when you have touched people. I am still not confident though, you just have to learn how to cope with it.

"I will miss the everyday discipline. I don't know if I will be able to push myself. The great thing about this job was you exercise straightaway each day and you are being paid for it. Much easier!"