British and Egyptian forces occupied the Sudan in 1898 and the following year the territory became an Anglo-Egyptian Condominium. This continued up until 1953, at which point the UK and Egypt agreed that Sudan should be granted independance. Sudanese Independence was granted on 1 January 1956. During this period, passport holders were treated as royal prerogative BPPs (British Protected Persons).
Click here for more information on the status of a British Protected Person (based on birth in a British Protected State or a British Protectorate).
Since 1 January 1956, Sudan is considered as a Foreign Country.