United Kingdom - Passport & Nationality - British Citizenship by Double Descent (Colony Birth PGF)
After 1948 and prior to 1983, British Citizenship could be passed two generations by Descent where the applicant was born in a place which at the time was a British Colony.
This solution requires the applicant to have been born between 01.01.1949 and 01.01.1983. Theior paternal grandfather must have been born in the UK.