Concentration camp or no, it's still the NHS. We're talking about an organisation that in real life took years to notice a Nurse was murdering patients in a hospital.
Yeah, in fact that was one of the most realistic parts of the story. That and the fact Esther was able to sneak in too. The more "silo'ed" an organization gets, the easier it is, really. And anyway, the ending of the episode pretty much says to me someone let Gwen infiltrate and all the other stuff she got away with doing anyway.
Alex