I love this show (and rarely say that about anything on the screen; large or small).
it's good enough to have come from the BBC, unlike the vast majority of the violence-laden dreck produced in North America (specifically Netflix).
The characters are human, like you and me, and go through life making mistakes learning stuff ... like the rest of us.
Most of all, I think, it's about kindness. In this era of combativeness on numerous levels (off screen: racial, gender, political, interpersonal, economic), this show is a great reminder that we can be kind to each other ... no matter what our differences may be.
If we don't see a Season 4, how about a movie?!