Victorian cottage query

Can anyone tell me why someone would lay concrete in the hallway of an 1890 Victorian bluestone cottage? It is carpeted over and has one room original boards that i can tell. The hallway is now 15mm higher than rooms that come off.

sometimes people panic with old houses and in a misguided attempt to prevent issues such as rising damp they fill the floor with concrete. From what I've read so far this is a poor idea and certainly not a solution. Concrete doesn't move or breathe, whilst the old Victorian houses were built on a system of lime render etc that allowed passage of air. Breathability is crucial to maintaining the dryness of these houses. Have you noticed any water damage near the concrete hallway?

Difficult to give a responsible assessment over the internet without any photos etc. IMHO your best bet is to get a Heritage consultant to assess. And yes I mean HERITAGE consultant. Many if not most builders do now know or understand how these old building systems work.