Eva Green was on a whole other level with the acting job she did on this show but Rory Kinnear was also amazing as Frankenstein's Monster/John Clare; Simon Russell Beale added such depth to what could've been a joke character in Ferdindand Lyle; Helen McCrory and Timothy Dalton were great.
And Billie Piper did great work too which surprised me a bit. I'd put Piper's monologue in Memento Mori where Lily drops the façade and reveals her true self to John Clare to be up there with some of the best work in the whole series.
or
no inbetween