He speaks about the opening 2 parter, series 4 in general, Merlin's identity and Uther's importance below:
"The first story is very much the story of Morgana’s revenge. We left Morgana in a terrible state at the end of the last series, and at the beginning of this, the two-parter, is very much about her trying to get her revenge on Camelot. She does quite an extreme thing, and it’s the question of whether Arthur and Merlin and Knights will be able to defeat her.
Series four goes to some very interesting dark places, but the great thing about the format of the show is you can always counter balance that with a lot of humour. So I think this year instead of having sort of stand-out comedy episodes, it’s very much about having lightness and darkness within episodes.
Merlin’s identity and whether his magic will be found out is a huge part of the next series. I think the audience is slightly obsessed with it. There are other reasons now for him not to tell people that he has magic. There are other people who want to know who he is, and you learn about the legend of Emrys. That’s a huge part of the next series: will his magic be found out? The net is closing in on him. There are other bigger and more important reasons why he can’t reveal his identity yet.
Anthony Stewart Head is an important part in the series and Uther’s legacy is important. There are some very exciting stories for his character. Some interesting choices and some unexpected choices.