IT started as a interval piece for the 1994 Eurovision Song Contest, but the seven-minute slot began a worldwide phenomenon.

Bill Whelan’s music combined with the energetic Irish dance to overshadow the whole contest. (Go on, who won Eurovision that year? Actually, it was Ireland.)

The producers, Moya Doherty and John McColgan, realised they had something and brought in a team of experts to produce a show based around the original performance, and so was Riverdance born.

It made a huge star of choreographer and chief male dancer Michael Flatley, who went on to create his own shows, but the original show is still touring the world 21 years after the first performances in Dublin in 1995, and the 21st anniversary tour will visit York Barbican from Tuesday to Thursday.

Executive producer Julian Erskine was one of the experts brought in at the start and he is still in charge, overseeing every aspect of the production. Even he had no idea how the show would dominate the entertainment world. “The original plan was to do a month in Dublin, but the truth of it was, it just took off," says the softly-spoken Irishman.

"The whole month of shows sold out before it opened, just based on that seven-minute piece.”

York Press:

Riverdance executive producer Julian Erskine

Riverdance may have been Irish entertainment but it proved popular everywhere. "That’s right. There was a phenomenal reaction and a London promoter called Barry Clayman said that we had to bring the show to London, and the same thing happened there," says Julian. "Nowadays, as well as the Riverdance troupe touring the UK and Europe, we also have one in North America.”

In Britain alone, the show has been seen by nearly three million people in well over 1,000 performances. Analysing why Riverdance has enjoyed such sustained success, JUlian says: "I think one of the reasons is that people come to the show over and over again, and then they bring friends who bring their friends and so on. Also we keep it fresh, with changes in the presentation as well as some of the numbers.”

This time around, there are two new numbers. "We also have a lot of new performers in the show, some of whom were not even born when the show started, plus we have added some new lighting and costumes. We spend a lot of time on the quality of the show,” says Julian.

As well as the original Riverdance piece that closes the first half, one mainstay of the production is the dance-off between the Irish dancers and the American tap-dancers.

York Press:

Leap to it: Riverdance on tour

“That one, and the flamenco dance, was in the original concept. I thought at the time that just Irish dance wouldn’t be enough, but the other styles allow the Irish dances to shine; and of course flamenco has a strong Celtic feel,” says Julian.

Was the dance-off a conscious effort to show both the differences and similarities in the styles? “I couldn’t have put it better myself. There’s the loose-limbed US jazz and the stiffer Irish styles. Don’t forget that all these styles got together when all these nationalities were immigrants in America and there was a lot of mixing,” says Julian.

Despite the physicality of Riverdance, very few injuries have been suffered by the dancers. “Yes, that’s right. They look after themselves and we have a team of masseuses and physiotherapists," says Julian.

"We do get the odd accident, but we can put those dancers in another part of the show; ‘light duties’ as it were. Plus we rotate the dancers; for instance, if a dancer injures their ankle, we can put them in a section where there's less strain on the ankle while they heal.”

Given the hard work involved, you might expect there would be a big turnover in dancers. “Not as much as you’d think," says Julian. "We had one girl start in 1994 and was with us for 19 years, and we have had some dancers stay for about 16 years. However, I’d say the average is five to six years.”

The 21st anniversary tour will travel around Britain for seven weeks, with up to eight shows a week, before the dancers head for Germany. No major alterations are planned to the Riverdance format for the anniversary.

“People love Riverdance the way it is, so we don’t do radical changes," says Julian. "If it ain’t broke, don’t fix it.”

Riverdance, 21st Anniversary, York Barbican, Tuesday to Thursday, 8pm, and 2.30pm Wednesday matinee. Box office: 0844 854 2757 or yorkbarbican.co.uk

By Martin Hutchinson