William signed the birth register entry for the third-in-line to the throne at Kensington Palace this morning.
George was born on Monday last week at St Mary’s Hospital in London. His name was announced two days later.
While most new parents have to travel to a register office to formally register the birth of their child, Westminster City Council registrar Alison Cathcart travelled to Kensington Palace for William to carry out the task.
A brief statement from the palace said: “The Duke and Duchess of Cambridge have formally registered the birth of Prince George.
“The Duke of Cambridge signed the birth register at Kensington Palace this morning, witnessed by a Registrar from Westminster Register Office.”
The register entry from which the birth certificate is produced was filled in by the registrar and signed by William. It gives the date and place of Prince George’s birth and his full name as His Royal Highness Prince George Alexander Louis of Cambridge.
William’s full name, His Royal Highness Prince William Arthur Philip Louis Duke of Cambridge, is also given, along with his place of birth in Paddington, Westminster - he was born at the same hospital. His occupation is listed as Prince of the United Kingdom.
His wife’s full name is given as Catherine Elizabeth Her Royal Highness, The Duchess of Cambridge, with her occupation described as Princess of the United Kingdom.
Her place of birth is listed as Reading, and her maiden name of Middleton is also included on the document.
The couple’s “usual address” is given as Kensington Palace, London.
The certificate is signed by William, as well as Ms Cathcart, whose title on the document is given as deputy registrar.
Ms Cathcart, who has been Westminster City Council’s superintendent registrar for 22 years, has presided over several celebrity marriages including Sylvester Stallone, Joan Collins, Barbara Windsor and comedian David Walliams.
She said: “It was of course a great pleasure to work with Kensington Palace in arranging the signing of the birth certificate for Prince George.
“This cements an association with Westminster City Council and royal births in the borough that goes back decades. We registered the birth of the Queen and Prince Charles and Princes William and Harry so it’s great to see that tradition continue.
“We can now add Prince George to that collection and again congratulate the Duke and Duchess on the birth of their son.”