Some of the things the Covid pandemic has taken away are easier to quantify than others. The death toll and the job losses make headlines, but the closed arts venues, the lack of shared creative experiences, not so much. But make no mistake, the arts face an unprecedented crisis. HARDtalk's Stephen Sackur speaks to Tamara Rojo, the internationally renowned dancer and artistic director of the English National Ballet. Can the performing arts withstand the Covid calamity?