to enrol: Persons over 18 years of age British citizens or people with a right of abode in the UK, or nationals of an EEA State or Swiss nationals Permanent residents of the United Kingdom (e.g. Indefinite Leave to Remain) Valid entry clearance holders (Visa holders) with at least 2 months of validity left on the entry clearance Short term visitors entering the United Kingdom (not needing visas) who were granted entry as a visitor on at least two occasions in the last six months, or four occasions in the last 12 months Exempt from UK Immigration controls or permitted to enter or remain in the UK for more than six months and have more than two months left of that permission Families of EEA state or Swiss nationals based in the UK or exempt from immigration controls and based in the UK See also ePassport gates (another type of automated self-service barriers that replaced IRIS and is used by the UK Border Force at a number of airports and train stations) Iris recognition Further Information Latest IRIS Information from UK Border Agency References Biometric databases Borders of the United Kingdom Databases in the United Kingdom Expedited border crossing schemes Human iris