If you're a royal watcher, you know that the Duchess of Cambridge gave birth today. If you'd like to say 'Congratulations' to Kate Middleton and Prince William on the addition to their family or to send greetings to Prince Charles on the birth of his grandchild, here's their mailing address:

Clarence House
London SW1A 1BA

Kate Middelton and Prince William are addressed as 'The Duke and Duchess of Cambridge.'

Prince Charles is addressed as 'The Prince of Wales.'

Congratulations to the parents and grandparents and happy birthday to the bouncing baby boy!

More info available here.