Police support unit (United Kingdom)
A Police Support Unit or PSU is a unit of police officers who have undergone specialist tactical training in Public Order and Riot Control. == About == Police Support Unit training in the United Kingdom is voluntary tactical training undertaken by selected candidates that provides students with the skills required to safely and effectively deal with a variety of public order situations outside the remit or capability of regular divisional officers.
Source: Wikipedia — Police support unit (United Kingdom) (CC BY-SA 4.0)