An indigenous person born and raised here who is decended from generations of ancestors who have for thousands of years worked, fought and died to protect this great land. Not a foreigner who's just got off a plane at Heathrow, the underside of a truck at Dover or a banana boat in the 50's.
I concider myself British because I can trace my family tree in this country back some 400 years. My grandparents fought in WW2 and my great grandparents in WW1. I would not concider myself British if I was born and could trace my family roots in another country and merely came to this country in order to find work or improve my quality of life. Equally I would not claim to be, or expect to be recognised as Indian if I upped sticks and moved to Delhi, or Nigerian if I moved to Abuja.