While the showrunner did stress “there’s plenty more to come,” he did admit he always thought of the show as a four-season story.
Vanstone explained: “I think that when we started the show, we had in mind arcs for these characters that took them across a number of series.
“Initially, it was kind of four series. But everything in this show plays out slower than you think it would.
“I think in other shows, you sort of risk the need to have more stories and more action and more things happening, but with our show, it’s the antithesis of that. We kind of give everything time.”
source: express.co.uk