They should have limited it to one series.
As a massive fan of both Mark Strong & Daniel Mays, it pains me to say this but even their superb talents are wasted on Series 2.
It seems that the under-underground Temple is getting more footfall than the station above it, with every new episode seeing at least one additional person discovering its existence.
The idea of extending Dr Miltons illicit surgery to service Rhys Ifans underworld character, Gubby was a good one, but handled.poorly imho, ditto his episode-by-episode plate-spinning and the writers definitely run out of steam. As had I by episode 4. Sorry.