British Nationality could be obtained through your birth, or through the birth of any one of your parents or grandparents, in Saudi Arabia. This arises because of Britain's relationship with the Arabian Peninsula and Britain's Colonial history.
To determine what form of British Nationality you might have, an analysis of your family's history must be done, and then applying it to the Nationality laws governing Saudi Arabia that have been passed over the years.
STATUS OF SAUDI ARABIA
Between 1535 and 1919, the Crown exercised extra-territorial jurisdiction.
From 1919, Saudi Arabia was considered a foreign country.