The atmosphere in the hair and makeup department backstage at the Britain's Got Talent studios in London is electric this afternoon, as a troupe of young Welsh dancers get ready to perform in tonight's semi-final. Troll Dancers, made up of 30 six to ten year olds from TDM Stage School in Sandfields, Port Talbot, first auditioned for the nation's biggest talent show in January.

After wowing the live audience and the judges with their colourful performance full of fun, they were soon invited back to compete in the semi finals. Tonight, they'll be dancing their hearts out in the hopes of impressing viewers at home who have the power to send the evening's most-voted performer straight to the final.

The judges will then be tasked with choosing a second act to go through to the final from the next two most-voted acts. Speaking to WalesOnline from backstage, principal and founder of TDM Stage School Terry Michael explained how the group's unique and fun concept came about.

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Terry said: "They're all fans of the trolls [Dreamworks' popular animated comedy]. They wanted to do something fun and upbeat and they picked the theme.

"They first auditioned back in January and after getting through, we've been rehearsing for the semi final ever since. The routine is really bright, upbeat and fun!

"At the moment [4pm], they're in hair and makeup. They'll be really bright and colourful, it's all about trolls and troll land! They're so young, they're really excitable at the moment!"

A parent of one of the dancers, Lowri Bennett, said Britain's Got Talent has been a "brilliant experience" so far, adding: "All producers, the show, everything's been fantastic." She added the programme is "phenomenal" and "out of this world" and "something you don't get to experience in your average day life".

At their audition, Troll Dancers gave a brilliant and entertaining performance to the song September by Earth, Wind & Fire. Judge Bruno Tonioli told the group that he "really wanted to join in" and described them as a "dazzling, sparkling, visual treat".

Head judge Simon Cowell joked: "I didn't think it was great... I thought it was brilliant!" TDM Stage School is no stranger to the Britain's Got Talent stage and has seen great success with many of its dance teams, including its Nu Sxool team going all the way to the grand final in 2012 and Notorious dance group getting through to the semi-finals last year.

Of course, Troll Dancers hope to follow in the footsteps of their classmates' success - and go all the way to the top. Terry added: "[BGT] is an excellent opportunity for them. We've had some fantastic opportunities for our dancers from previous series, some have travelled the world.

"We're just hoping that they [Troll Dancers] can have the same success."

The third semi-final of Britain's Got Talent (the episode with Troll Dancers) airs tonight, Wednesday May 29, on ITV1 from 8pm to 10pm. During the episode, the phone lines will open for UK viewers to vote for their favourite act.