Why has Merlin run and run where Robin Hood, for example, did not? I don't really feel any huge qualitative difference between the shows. Maybe it's just dumb luck. Or perhaps I'd need to watch more than one and a half episodes of each. Any experts out there?
Here's the promo for the imminent fifth series of Merlin. As I understand it, this is what the BBC are going to broadcast on Saturday evenings between the first and second stretches of the new Doctor Who series.