Royals Kate Middleton and Prince William's New Royal Titles Just Became Official — Here's Why King Charles declared his son Prince William to be the Prince of Wales, the traditional title held by the heir, just one day after he became monarch By Stephanie Petit Stephanie Petit Stephanie Petit is a Royals Editor, Writer and Reporter at PEOPLE. People Editorial Guidelines Published on February 24, 2023 12:30 PM Share Tweet Pin Email Prince William and Kate Middleton's titles as the Prince and Princess of Wales are now official. Just one day after the Sept. 8, 2022, death of Queen Elizabeth II, King Charles III gave his first speech as the United Kingdom's monarch. In the televised broadcast, the new sovereign announced that his son Prince William would be the new Prince of Wales and his daughter-in-law Kate would become the Princess of Wales. However, the royal titles only became official this month, when the Letters Patent passed the Great Seal of the Realm on Feb. 13. The full notice from the Crown Office was printed in The Gazette on Friday. Prince William and Kate Middleton at the BAFTAs 2023. Chris Jackson/Getty The announcement read in full: "In accordance with the direction of HIS MAJESTY THE KING Letters Patent have passed the Great Seal of the Realm, dated the 13th February 2023 for creating His Royal Highness Prince William Arthur Philip Louis, Duke of Cornwall Rothesay and Cambridge, Earl of Carrick and Strathearn, Baron of Renfrew, Baron Carrickfergus, K.G., K.T., Lord of the Isles and Prince and Great Steward of Scotland, PRINCE OF WALES and EARL OF CHESTER." Why Kate Middleton and Prince William's Household Will Be Divided This Weekend Queen Camilla, King Charles, Prince William and Kate Middleton. Chris Jackson/Getty Prince William, 40, and Kate, 41, were given the titles of the Duke and Duchess of Cambridge by Queen Elizabeth on their wedding day in 2011. When they were proclaimed the Duke and Duchess of Cambridge, the couple simultaneously became the Earl and Countess of Strathearn as well as Baron and Baroness of Carrickfergus, although those titles were used less often. Immediately following the death of Queen Elizabeth, William and Kate's Twitter and Instagram accounts were updated to state they belonged to the "Duke and Duchess of Cornwall and Cambridge," as the title of the Duke of Cornwall is traditionally held by the eldest son of the reigning British monarch, with his wife taking the Duchess title. Prince William and Kate also became the Duke and Duchess of Rothesay, titles previously used by Charles and Camilla, applied when they are in Scotland. William and Kate retained their Cambridge titles. Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more! Prince William and Kate Middleton. EDDIE MULHOLLAND/POOL/AFP via Getty However, the Prince of Wales title is not automatic and must be bestowed by the monarch. The legal instruments known as letters patent are an open document from the monarch used to express the sovereign's will, such as "to confer an office or create a new peerage," according to the Royal Collection Trust. Now, the letters patent making Prince William the Prince of Wales passed the Great Seal of the Realm. Along with becoming the Prince of Wales, the letters patent also decreed that William is granted the title of Earl of Chester. That makes Kate the Countess of Chester. July 1, 1969: Queen Elizabeth II crowns her son Charles, Prince of Wales, during his investiture ceremony at Caernarvon Castle. Hulton Archive/Getty Charles, now 74, was just 3 when his mother, Queen Elizabeth, acceded to the throne. He was not formally pronounced the Prince of Wales until he was 9, and the Investiture of the Prince of Wales — when Charles was presented to the Welsh people as their prince — took place at Caernarfon Castle in 1969 when Charles was 20. How King Charles and Queen Camilla Will Make Royal History at Their Coronation This May Such a ceremony is not expected to take place for Prince William, but he will likely play a role in King Charles' coronation on May 6.