http://www.tvmaze.com/shows/3369/beowulf-return-to-the-shieldlands
TVMaze, IMDb and wikipedia say there are only 12 episodes, but Amazon Prime shows 13 episodes available for streaming:
Is this an additional episode, or have Amazon edited the show to stretch it out across 13 episodes?
If it's an additional, we'd add the episode with no airdate.
If it's edited we wouldn't add the episode as the Network is ITV, not Amazon.
Judging from the episode summaries, the extra episode is Amazon's episode 9. It's summary is a second paragraph of ITV's episode 8 summary. Which is awkward, because the runtime of all episodes are the same, ~44'. Looks like Amazon version is somehow extended.
BTW, the original ITV press release mentioned 13-episode order.
https://www.itv.com/presscentre/press-releases/itv-commissions-13-part-epic-warrior-drama-beowulf
To add to the confusion Amazon UK have 12 episodes.
ITV Studios (which produced the series) have 13x60' episodes https://itvstudios.com/programmes/beowulf-return-to-the-shieldlands
Ok, here's the answer from the official Facebook account (as official as it gets):
12 in UK
13 in USA
Originally, it was planned to air on Saturdays. But due to programming cuts it had to be moved to a Sunday. Which meant the time slots had to be different. So they amalgamated episode 8 & 9 into one. In USA they get the full series.
Itv did cut 2 episodes in 1, so thats why we have 12 episodes.