When does Merlin return?

Merlin (also known as The Adventures of Merlin) is a British fantasy-adventure drama television programme. It was broadcast for five series on BBC One between 20 September 2008 and 24 December 2012. The programme starred Colin Morgan, Bradley James, Katie McGrath, Angel Coulby, Richard Wilson, Anthony Head, and John Hurt. It is a reimagining of the Arthurian legend, in which young warlock Merlin is sent to the kingdom of Camelot by his mother because of his "special gift"