This has to be one of the most well-written shows ever.
It's about two brothers in the "modern" merchant's world, but that's not why it's well written. Somehow, it manages to hint at something, but so subtly you wouldn't notice. That way, when something happens involving it, it is always brilliant.
My only gripe is that it requires you to watch most of the episode to enjoy it.
That aside, it really is a timeless classic. In today's world of Little Britain and Catherine Tate, it provides a welcome relief. I just wish we'd spend more time and money on proper comedies like this...