Watched episode 1 of Good Omens. I read the book by Neil Gaiman and Terry Pratchett about 25 years ago and so can't really remember it, but the episode was really entertaining.
An angel, Aziraphale (Michael Sheen) and a demon, Crowley (David Tennant) have been on Earth since Genesis and have grown to love all things Earthly - wine, music, clothes, food etc. All of a sudden Crowley has to begin the process of Armageddon. The son of Beelzebub is sent to Earth. Mix ups with Satanic nuns occur and plans go awry. It's great stuff. I can watch David Tennant in anything. Here he is channelling Bill Nighy for large chunks. Sheen is great too - completely different from his portrayals of Brian Clough and Tony Blair.
If you like it you should consider listening to David Tennant Does a Podcast where he interviews actor friends and others. His chat with Olivia Colman is wonderful.