amuel Staples, a fresh-faced 20-year-old from London's Guildhall School of Music & Drama, appears nonchalant.His black leather jacket is off and he's raring to go. His excitement is palpable. He's been playing the violin since he was five, but this is the first time anyone has let him loose on a Stradivarius for a day and "every violinist," he says, "dreams of playing a Strad."