Running time: 111 mins. Starring: Zac Efron, Corbin Bleu, Vanessa Hudgens, Monique Coleman, Ashley Tisdale, Lucas Grabeel, Olesya Rulin, Alyson Reed.

Already breaking box office records in the UK for advance ticket sales, the third instalment of the Disney Channel phenomenon takes a bow on the big screen for the first time, bidding a tearful farewell to most of the actors who have made the series such a toe-tapping success.

The senior class of East High School prepares to graduate and go to different colleges around the country. Troy Bolton (Zac Efron) and best buddy Chad Danforth (Corbin Bleu) are looking forward to playing basketball together, on opposite sides of the country to their respective girlfriends Gabriella Montez (Vanessa Hudgens) and Taylor McKessie (Monique Coleman).

The attention-seeking twins Sharpay (Ashley Tisdale) and Ryan Evans (Lucas Grabeel) hope to achieve the fame and adoration they have always craved. As the teenagers prepare to say goodbye to one another, they agree to take part in one final musical, inspired by their lives As usual, Sharpay tries to steal the limelight, plotting with her brother to woo talented composer Kelsi Nielson (Olesya Rulin), who always writes the best songs for lovebirds Troy and Gabriella. When ebullient drama teacher Ms Darbus (Alyson Reed) confides that two guests from the world-renowned Juilliard performing arts conservatory will attend the performance to award a scholarship to one of her students, the perky classmates pull out all the stops to ensure a standing ovation.

Unless you have been living in a cave for the last fortnight, you won’t have escaped the buzz around this picture.

What started out as a modest TV movie back in January 2006 has fast become a global phenomenon.

At the London premiere, thousands of young fans skipped school and queued for hours to get a glimpse of the show’s fresh-faced stars Zac Efron, Vanessa Hudgens and Ashley Tisdale.

For anyone who doesn’t have HSM-obsessed children, it’s hard to understand the fuss about the squeaky clean musical extravaganza.

It’s almost Grease-lite – no smoking, swearing or sex, but plenty of colour, catchy tunes, soppy lines and spine-tingling dance sequences.

Vanessa, who plays one half of the romantic leads Gabriella and Troy (Zac), sums it up neatly: “Kids can relate to us and our characters. They’ve been to school with the Troy, the Gabriella and the Sharpay (Ashley) and they look up to us in a sense because it is a world where there is no sex or drugs or violence, it’s just a movie that makes you feel good.”