The comprehensive agreement (SI 1977/1719) has effect
a) In the United Kingdom for
i) Income Tax from 1975-76,
ii) Capital Gains Tax from 1975-76,
iii) Corporation Tax from 1 April 1975.
b) In Sudan for any year of assessment beginning on or after 1 January 1975.
The text of the Tax Treaty can be found via https://www.gov.uk/government/publications/sudan-tax-treaties