These statistics are published by the Health and Safety Executive. They come from the 2015/16 Crime Survey for England and Wales (CSEW).
The CSEW measures respondents’ experiences of crime-related incidents and classifies these into offence types (including physical assaults and threats). It also collects detailed information about the nature of the victimisation.
The CSEW defines violence at work on the basis of type of offence (assaults or threats), what the victim was doing at the time of the incident (at work or working), and the relationship between victim and offender (domestic violence is excluded).