Ballet would have been an obvious revenue stream for Sadler’s Wells when it reopened back in 1998 but straight-up classics have been few and far between over the past two decades — the Rothbart of the Royal Ballet of Flanders’ Swan Lake wore a live owl on his head. And yet, while the theatre’s programming fights shy of tutus and toe shoes, its fiercely contemporary output can sometimes bridge the notorious gulf that has traditionally divided classical and contemporary audiences.