I know this is in jokes, but when Alistair McGowan DID go on "Who do you think you are" in 2007 he found he had Indian ancestors.
His father was born in India and his father came from mixed British / Indian parentage.
When the British "ruled" India they encouraged British men to marry Indian wives so it would produce a group of children who would grow up and be loyal to the British and be happy to work for them.
Many of these children were then given jobs by the British when they grew up.
Because the indian people married British people they took the British surname, so there is now a whole group of Indian people living in India with "British" surnames.
Alistair went out to India to meet some of his ancestoers and it was strange when he went to one house where the sign on the gate was "McGowan" but when he went in the house the people were all Indian.
I have to say it was a very interesting program.
More here
http://en.wikipedia.org/wiki/Alistair_McGowan