I am a native British English speaker and fluent in French. That means that when I speak and write in English, I sound English, and when I speak / write in French you can occasionally hear that I have a very slight accent. I learned to speak French before I could speak English, but because I have lived in the UK since I was 3 the English became the dominant language in my brain - use it or lose it, basically. I teach ESL in Japan. Not sure if that's altogether relevant, but I thought I'd just throw it in there just in case.