Guardsmen play 'Congratulations' for royal baby
23 July 2013 Last updated at 12:22 BST
Guardsmen have played 'Congratulations' to mark the arrival of the Duke and Duchess of Cambridge's baby son, ahead of the Changing of the Guard.
Royal watchers and tourists have been queuing in the rain to catch a glimpse of a bulletin announcing news of the birth, which is being displayed on an easel there.
People across the globe have been celebrating too, including parties in Japan, cannons being fired in New Zealand, and billboard announcements in New York.