British Nationality could be obtained through your birth, or through the birth of any one of your parents or grandparents, in Turkey. This arises because of Britain's relationship with Turkey 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 Turkey that have been passed over the years.
STATUS OF TURKEY
Up to 06.08.1924, the Crown exercised extra-territorial jurisdiction over Turkey.
From that date onwards, Turkey was an independent foreign country.