Jon Hamm has joined the cast of Good Omens, the upcoming television adaptation of Neil Gaiman and Terry Pratchett‘s novel Good Omens: The Nice and Accurate Prophecies of Agnes Nutter, Witch, Amazon Studios and BBC announced today.

Hamm, who’s best known for his leading role in TV’s Mad Men and was seen earlier this year in Edgar Wright’s Baby Driver, will be playing the role of the archangel Gabriel, who is the primary messenger of God, in the upcoming six-part limited series.

Filming has begun in London on Good Omens, the limited television series from Amazon Studios based on the Neil Gaiman and Terry Pratchett novel Good Omens: The Nice and Accurate Prophecies of Agnes Nutter, Witch, and Gaiman has revealed today the first look at its stars David Tennant and Michael Sheen in character.

Check out the full image here below of Tennant and Sheen on set from the opening scenes shot at St. James Park in London.

At the start of the year it was announced that Amazon Studios had ordered the limited series Good Omens. The series is based on the Neil Gaiman and Terry Pratchett novel Good Omens: The Nice and Accurate Prophecies of Agnes Nutter, Witch.

Now comes the first casting news. It’s being reported that David Tennant (Doctor Who, Jessica Jones) and Michael Sheen (Masters of Sex, Frost/Nixon) have joined the cast.

More below, including a description of the series.

Amazon Studios has announced that they have ordered Good Omens, a TV series adaptation of the late Terry Pratchett (“Discworld” book series) and Neil Gaiman‘s (American Gods) Good Omens: The Nice and Accurate Prophecies of Agnes Nutter, Witch.

The adaptation will be a limited comedy series, which will run for six hour-long episodes. It will premiere in 2018 exclusively on Amazon’s Prime Video all around the world, and will air on the BBC in the UK sometime after its Prime premiere. Co-producing is BBC Studios along with Narrativia, the production company launched by Pratchett in 2012, and Gaiman’s The Blank Corporation, in association with BBC Worldwide.