I think it's only supposed to be around 50 minutes. It's just had the end credits removed is all.
Episode 2 seems to follow straight on. I don't think anything was cut, and I haven't seen a longer version.
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Oh, the series was created by
Chris Chibnall, who is the showrunner & head writer. He was previously the head writer on Torchwood, and has also written for Doctor Who and Law & Order UK.