SERIES PREMIERE: This new BBC America series is like FX’s The Americans, except it’s about British spies on home soil, and takes place in the early 1970s. Tom Hughes stars as a young agent who’s very dedicated, but not infallible – as we can see immediately, from the first of a series of dramatic flashbacks. The drama is deliberate and multi-layered, like a Tinker, Tailor, Soldier, Spy study, and the co-stars include Brian Cox, the MI-5 leader who goes by the name of &ldq