Shall we dance? Just try stopping us!

On stage, a dozen of the world's most talented dancers are performing pirouettes and pliés. Their costumes sparkle, but over them are draped adidas tracksuit tops and sweaters. Beneath crystal-sequinned skirts are multi-coloured stripy woollen leggings.

It is 15 minutes before the curtain rises on the first night of the English National Ballet's production of Strictly Gershwin at the London Coliseum, and the audience's anticipation is causing a frisson of excitement among the dancers. That said, the atmosphere is surprisingly laid back.

Lauretta Summerscales, 20, who performs a solo in the opening number and makes no bones about her ambition to become a principal dancer, is limbering up and stretching. "I have to keep my body going or my calves get really tight," she says. Although this is a first night at the Coliseum, the show has already been on tour, and she is calm. "This feels like another rehearsal, because we've done so many shows," she says.

"If I'm performing a role I haven't rehearsed much, I get really anxious. And I do still get worried if there's something that technically I'm not very good at. I sometimes get myself worked up. But a principal once told me: 'The audience don't care if it's your first time in a role, or if you've never danced with your partner before – just get on and do it.' I think it was the best bit of advice I've had."

Lauretta went to Oakfield school in Surrey until she was 16, practising ballet at her mother's dancing school. After GCSEs, she won a place at the English National Ballet School, and was offered a contract after two years in the corps de ballet. "It proves you can be normal and English, and still make it," she says. The company of 67 is made up of a mixture of nationalities: British, Russian, Japanese, Cuban, Spanish, French and Australian.

The dancers have just finished a four-week Christmas run of The Nutcracker. "This has a totally different feel, and I think it helps us get a lot of energy back. We normally see the cast going down by the end of the Coliseum season with a few injured people, so casting gets more manic." She says she is so used to hearing strings that it is refreshing to be dancing to the saxophone and drums on stage. "The music is so amazing: I grew up with Gershwin."

Barry Drummond, a member of the 38-strong corps de ballet, says: "There's an added buzz on the opening night. If you're not at all nervous, you're not taking it seriously. This ballet is more about style. It's very different from The Nutcracker."

Unusually for a ballet, the orchestra is on stage. As the curtain rises, the conductor starts to dance. In the wings, the dancers are bobbing about to Gershwin music, the atmosphere upbeat. There are tap dancers and Swarovski crystal costumes, roller skaters and a big band feel. Understudies practise the moves in the wings in time with those on stage.

There is an ethereal magic when watching the ballet from the audience: a feeling that you never want the curtain to come down or the beauty to end. The atmosphere backstage is a more down-to-earth sort of magic. One corps member runs off-stage exclaiming: "I hit my head," while another pair, who have apparently missed a step while dancing together, run off bemused, asking each other: "What happened there?"

The dancers may be dedicated and single-minded, but there's a strong team spirit. There are giggles, but scant evidence of ego. One offers to teach another the moves for her role, as they will swap over in two days' time. The sense of camaraderie is comparable with that of a top football team. There is even graffiti in the loos, but, inevitably, it is rather genteel, contributors asking what a piece of peeling paint resembles: "A map of England?" "A Father Christmas?" Above, another scribbler has added her own graffito, criticising writing on the walls: "This is the ENO, not a brothel." "Really?" another replies.

Unlike your average workplace, everyone in this office is physically perfect. But the leaving card circulating for signatures has a familiar feel, as do the banter and the griping, albeit in a variety of accents and languages.

Before they go on stage, senior principal dancer Daria Klimentová, 40, practises in the corridor with Vadim Muntagirov, 21. They have been performing together for the past two years, one of the most unusual partnerships in ballet today. Despite the age gap, they are perfect together and do not want to dance with anyone else. When their bodies are in motion, no one notices the age difference.

When Daria, from the Czech Republic, first met Vadim, from Russia, she was not convinced. "He had just left school, I didn't think he was ready," she says. "But we slowly developed an amazing partnership: he inspires me and makes me really happy. It is very special: I have been dancing professionally for 20 years, and only now, at the end of my career, do I have this relationship. I am so lucky that I met him and it happened. We share the same sense of humour and have a shared culture. I take freshness from him, while he takes experience from me. He just keeps smiling at me and it makes everything much better."

She is starting to look to the future, though, and is considering becoming a director of a company or opening her own dance studio. She is a keen photographer and would like to develop her skills. "It's very individual when you stop dancing: if your body doesn't get stiff you can keep going."

Vadim has a whole dancing career ahead of him. "Two and a half years ago, I had never performed in a full-length ballet. I now work with the best ballerina here. I look forward to going on stage: I just want to be dancing with her."

As they go out to perform the pas de deux in Summertime, and lose themselves in their dance, I see Vadim smile at Daria, everyone in the Coliseum enchanted by the magic between them. In a few steps they are a world away from tracksuit tops and woolllen, stripy leggings.