The Duke and Duchess of Cambridge arrived in Cutty Sark, east London, for a lunchtime engagement where they will launch a new sailing competition taking place on August 9 to raise money for eight of their charities. William and Kate are set to go head to head in person in the King's Cup Regatta this summer, staged in the waters off the Isle of Wight, to raise awareness and funds for eight of their patronages. Related articles Royal baby at sunrise: Meghan’s baby boy born at EXACTLY daybreak Meghan Markle: How royal baby will be ‘poster boy for the new world... At today's launch, William and Kate, who donned a white-and-blue shirt paired with trousers, were greeted by Sir Keith Mills and the Commodore of the Royal Squadron, Jamie Sheldon. The couple took the chance to speak about Meghan and Prince Harry's first son, who was born yesterday at 5.26am. The Duke of Cambridge said he is "absolutely thrilled" about the news, and jokingly mocked his brother Harry saying he welcomes him "to the sleep deprivation society that is parenting". READ MORE: Royal Baby LIVE: Queen and Philip at rare Windsor Castle event as they see Meghan & Harry Kate and Prince William stepped out in London today (Image: REUTERS) The message shared by kensingtonroyal yesterday (Image: INSTAGRAM/KENSINGTONROYAL) The Cambridges welcomed the birth of Baby Sussex yesterday afternoon with a message shared on their Instagram account, kensingtonroyal. The couple said they were “delighted” with the news of his arrival and looked forward to meeting the baby boy. The message read: “The Duke and Duchess of Cambridge are delighted with the news of the birth of The Duke and Duchess of Sussex’s son today, and look forward to meeting the latest addition to the family.” Meghan and Harry’s baby is seventh-in-line to the throne and cousin to the Cambridges’s children, Prince George, Princess Charlotte and Prince Louis. Related articles Meghan Markle taken to £15k hospital: Why was Portland Hospital secret Meghan Markle news: How Meghan may upset the Queen over Baby Sussex Kate and William are in Cutty Sark, east London (Image: EPA) William and Kate said to be 'delighted' with the news of the birth of Baby Sussex (Image: GC IMAGES/GETTY) Among the hundreds of comments congratulating on Meghan and Harry for the happy event, one Instagram user cheered at Kate and William for becoming “uncle and aunty” of Baby Sussex. The social media user wrote: “Congratulations on the newly uncle and aunty and of course to the little royals of finally having their first cousin.” Kate and William have another nephew, Arthur Michael William Matthews, son of Pippa Middleton and James Matthews. Meghan gave birth to a healthy baby boy in the early hours of Monday, as revealed by Buckingham Palace, but only announced the joyous occasion to the public in the afternoon, after they informed friends and relatives. Prince William and Kate welcomed the birth of Baby Sussex with an Instagram post (Image: EPA) The birth was announced with a message shared on the sussexroyal Instagram account, which read: “We are pleased to announce that Their Royal Highnesses The Duke and Duchess of Sussex welcomed their firstborn child in the early morning on May 6, 2019. “The Duchess and baby are both healthy and well, and the couple thank members of the public for their shared excitement and support during this very special time in their lives. “More details will be shared in the forthcoming days.” “Their Royal Highnesses’ son weighs 7lbs 3oz.” All rights reserved for this news site express.co.uk and under his responsibility