Millie Bobby Brown: ‘I don’t underestimate myself any more’

The 22-year-old ‘Stranger Things’ star is back for a third time as Sherlock’s swashbuckling little sister. Alongside her director Philip Barantini and co-stars Louis Partridge, Himesh Patel and Sharon Duncan-Brewster, she speaks to Annabel Nugent about action, romance, and Enola’s importance to a generation of young girls – including Brown’s baby daughter