The Duke and Duchess of Sussex are to be congratulated on the safe arrival of baby Archie into one of the most exclusive clubs in the world. Of course, I am referring to the fact that he will be an American citizen. It is understood that his mother has not renounced her American citizenship and consequently Archie will be a ‘dual citizen’ of America and Britain.

All American citizens pay US taxes regardless of where they live. So, while Archie remains an American citizen he will have to pay tax in the UK (to his great-grandmother) as well as pay taxes to Uncle Sam.

He will not necessarily pay tax twice, as the UK wi...