This chapter shows how changes to officeholding shaped practices of arrest in the capital. It uses a new dataset to rethink established accounts of early modern policing based on widespread participation. Most arrests in London were made by men and, from the late seventeenth to the mid-eighteenth century, a growing proportion were made by officers. At the same time, constables and their colleagues acquired greater powers to arrest people on the basis of suspicion alone. These powers were frequently used against poorer women, who officers arrested on ill-defined charges of vagrancy, night-walking, or suspected theft. In the early eighteenth century one judge called for closer adherence to due process in such arrests, but this had little long-term effect.