The level of security checking for airside staff exceeds that which a Criminal Record Bureau (CRB) check on its own could provide. The Department mandates a regime which involves the confirmation of identity via an acceptable document, such as a valid passport, and verification of references for the past five years, including any gaps. This is supported by a check of unspent criminal records, available from the Criminal Records Bureau’s equivalent agency in Scotland. Additionally, airport staff who undertake a security duty, such as searching and screening passengers and baggage, are subject to national security vetting to counter-terrorist check level.