Katie McGrath (Morgana) has teased Merlin’s fourth series finale, The Sword in the Stone: Part 2, and offered some intriguing hints on how ends.

“The ending is the basis of one of the main myths,” she tells Digital Spy. “Not one that everybody’s familiar with, but it’s setting up a very powerful and pertinent myth that runs through the Arthurian legend.”

McGrath says everyone will be itching for Series 5 after the final scene which “sets up season five so brilliantly”.

“Before, you were [always] left on this lovely finishing note, because we didn’t know whether we’d be commissioned [for another series],” she said. “We know that we’re doing season five, so now this is just going to make you want it to be September next year and the start of the new season!”

She also spoke about the show continuing beyond Series 5: “It all depends on how [the writers] spin out season five and the legend,” she said. “There’s so many different interpretations [and] so many stories that they haven’t told.

“You want it, whenever it ends, to end on the right note. If that takes seven seasons, if that takes ten seasons… you want to tell the story properly.”