I worked as an HGV driver at the Prison Service depot just behind this building for 25 years until I retired. In the early years, the ground floor was our local office until maintenance became too expensive. Several years ago Supply and Transport head office in Corby was closed and the intention was to relocate here, but being a Grade II listed building, the cost of renovation was prohibitive, so they moved to Leicester instead! Up to about seven years ago, it was a job for one of the mechanics from the vehicle workshop by the gate to climb the tower once a week and rewind the clock. But then elf'n'safety deemed it to be too dangerous!
The pumphouse in the second picture is still operational and handles all the sewage and drainage for the whole site.
Be careful - it is Grade II listed and there is 24hr on-site security.