Wednesday nights, 11pm ish. I haven't actually managed to catch a whole episode yet, and they don't seem to be doing poscasts of it, which is a shame.
It's basically a monologue featuring a guy who's blatantly in love with the girl who's marrying his brother. He spends the most of each episode trying to pick up the pieces of the drunken destruction everyone around him causes. It's beautifully scripted and acted, really poignantly done.
http://www.bbc.co.uk/radio4/allbarluke/