British citizenship was not lost by anyone who became a citizen of these countries on that date.
The treaty process gave British citizenship to the "native" population.
However, it is not always possible to give up your British citizenship or nationality.
It remains home to 265,000 holders of full British citizenship.
One analysis suggested it would result in more than a million people being granted British citizenship.
He held several distinguished posts here and took British citizenship in 1939.
However, other rights can vary according to how the British citizenship was acquired.
"And we will take firm action against those who abuse the privilege of British citizenship to do so."
This included the boy's British citizenship conferred upon him when he was five.
You can find out more about British citizenship here.