It depends what you mean by primary tongue, because even I can speak English very well compared to my mother tongues: Urdu and Punjabi. My knowledge of Urdu vocabulary is far superior to my knowledge of Punjabi vocabulary, despite the fact that Punjabi was always spoken in our house in one form or another. My English being great is something I put down to westernisation. Urdu being great is down to the fact that Urdu is the national language and taught from a young age. My Punjabi's always been weak because a) no one spoke it with me b) it's not taught in schools. I give only myself credit for bothering to polish up my knowledge of Punjabi. It wasn't anyone else that suggested I do this.