Which person should join Spooks?

[JHyde]

Yeah, but Ruth's not a field officer. I mean, I love her to death, but her talents lie elsewhere, just as Malcolm's did.

I think Ros can recognize it, but that would be it. The same way I can recognize Tamil, for example, but I can't speak, I only catch certain phrases. I think you mean

Spoiler: show

in 5.6/7 when Ros was talking to the Mossad agent. She was just saying that his Arabic wasn't completely authentic because he sounded like a Yemini Jew she'd once known.