 The grade of Assistant Immigration Officer was revived in 1991 but the role was initially badly defined and the scope of their work subject to ongoing dispute with the unions representing the Immigration Service grades, the Public and Commercial Services Union (PCS), and Immigration Service Union (ISU).In 2017 immigration to the UK from outside the EEA is based primarily on the five tier system High-Value Migrant Tier 1 Visas, Skilled Worker Tier 2 Visas, Student & Tier 4 Visas and Temporary Worker Tier 5 Visas with applications being reviewed by an Immigration Officer.The working environment for the Immigration Service differed greatly dependent on whether the work was performed at a port of entry, or in an after-entry environment within the community.