As pointed out earlier.... what is a 'legitimate Brit'? If you are talking about ancestry of only a few hundred years then 50% of all Yanks are British

I'm white, but not British, I descend from the family of the 3rd Century High King of Ireland, that'll be Eire

White is not the natural colour of the original human race. Britian is a mix of a number of races, none of them 'British' which has never existed as a bloodline.

http://blogs.discovermagazine.com/gnxp/2006/09/blood-of-the-british/

http://www.prospectmagazine.co.uk/2006/10/mythsofbritishancestry/