Assured tenancy – this term refers to a form of residential tenancy, which applied in England and Wales. The assured tenancy has been established with the Housing Act 1996, where it is written that it grants a degree of security of tenure in favor of the tenant on the premises. This is needed because tenants sometimes need good protection for habiting the rented premises.
See also http://www.legislation.gov.uk/ukpga/1996/52/contents .