When not one but two street dance crews blasted into Britain’s Got Talent 2009, it felt like a pressure cooker blowing. An ardent, physical and excitingly exact form of dance that had been bubbling away, compressed and hidden, under the surface of British public entertainment exploded. Of the two, Diversity (the eventual winners) and Flawless, it was Flawless’s 10 men who had the almost scarily precise look of a serious dance company, and last night they crowned a massive year for them at the Royal Festival Hall, London, with a full-length show, Chase the Dream, that proves them to be fine instinctive entertainers as well as crack dancers.