Abstract: Research Question: To what extent could police identify victims of modern slavery among growers arrested on cannabis farms as suspects under drug laws, and what challenges of evidence would have to be met to separate offending from victimisation? Data: A purposive sample of criminal history data of all Vietnamese nationals arrested for cannabis cultivation offences in Surrey/Sussex in the 3 years to 2017 (N = 19) was identified and collected. Three ‘cannabis farm’ cases from the period 2014–2017 were analysed to produce key information about growers, including their nationality, criminal history and possible status as modern slavery victims. The case records and interviews provide key information about the extent to which growers on farms were treated as slaves under the 2015 Modern Slavery Act. Methods: Semi-structured interviews were conducted with the three arrested growers to explore their lived experiences of recruitment and labour on the farms. Arresting police officers were also interviewed to explore how they frame the problem of cannabis cultivation and make decisions about their role in confronting it. Interview transcripts were prepared for analytic purposes. All interviewees were informed that the research was focused on the management of the policing of cannabis farms alone and full anonymity was assured. Findings: Five of the 19 Vietnamese nationals had previous criminal disposals. Of the remaining 14 individuals, five had no record and nine had various charges, but the prosecutions had not reached court. Of the three cases examined in depth, the arrested growers provided stories consistent with their having been trafficked and subjected to ‘debt bondage’. They described precarious journeys before being forced to work on UK farms. All three had been exposed to threats of violence or death for themselves and/or their families, should they attempt escape. Varying levels of mental and physical hardship were evidenced. There were a priori reasons to conclude that they were eligible to be considered modern slavery victims. When arrested, however, none had pleaded victimisation. Police officers demonstrated an ignorance of related legislation and varying levels of awareness of the possibility of modern slavery. They responded to the first impression made by the grower as a person culpable under drugs laws. Even where officers had concerns about modern slavery, no appropriate crime was recorded, and no formalised investigation followed. Conclusions: Given reluctance or inability to frame the police response to cannabis farms under modern anti-slavery legislation, policing agencies should consider adopting more detailed practice guidelines to officers on how to react to the complex challenges involved, including the investigative opportunities that may help unearth modern slavery on cannabis farms through greater encouragement of victim accounts.