watching line of duty from beginning again, looking for clues!
I intended to post a fair bit about LoD last night, but I had network problems. I'll try to catch up with that tonight or over the weekend, but in the meantime...
With hindsight, there are big clues scattered around the earlier series, including quite a few in S1. I found this Radio Times article very interesting as a summary/reference [Spoiler Warning, obviously! ]: