Video report by ITV News Royal Editor Chris Ship
Congratulations for the Duke and Duchess of Sussex have been pouring in from across the UK and around the world, after Meghan gave birth to a baby boy around a week after her due date.
On Tuesday morning, the arrival of the Duke and Duchess of Sussex's baby son was celebrated during the Changing the Guard ceremony at Windsor Castle.
The Band of the Royal Regiment of Scotland, dressed in red tunics and bearskin hats, played the musical classic 'Congratulations' in the baby's honour.
Harry and Meghan have also asked the public to donate to four children's charities - Little Village, the Lunchbox Fund, Well Child, and Baby2Baby - instead of sending presents for the baby.
The new baby is seventh in line to the throne and the Queen's eighth great-grandchild.
Speaking on Monday, just hours after the arrival, the Duke of Sussex - who was present at the birth - said his new son, who was born at 5.26am on Monday morning and weighed 7lb and 3oz, "is absolutely to-die-for".
Speaking from Windsor Castle's Royal Mews he said the Duchess of Sussex and baby were both doing "incredibly well."
"It's been the most amazing experience I could ever possibly imagine," he added.
"How any woman does what they do is beyond comprehension, but we are both absolutely thrilled and so grateful to all the love and support from everybody out there."
The Queen, Prince Philip, grandfather The Prince of Wales and Prince William and Kate are said to be "delighted with the news", as are other senior members of the royal family.
Meghan's mother, Doria Ragland, is said to be "overjoyed by the arrival of her first grandchild" and was with the couple of Frogmore Cottage.
Buckingham Palace said the name of the baby would be announced in due course.
Who's reacted to the birth?
Meghan's former Suits co-star and onscreen love interest Patrick J Adams wrote on Twitter: "Just heard that the world just got heavier by 7 pounds and 3 ounces. Much love to him and his incredible parents. "
The London Eye turned red, white and blue in honour of the royal birth - Prince George, Princess Charlotte and Prince Louis' births were all marked in the same way.
The BT tower in London celebrated the royal birth by declaring 'It's a boy' and congratulating the couple on the happy news.
The Archbishop of Canterbury Justin Welby, who presided over the couple's wedding last year, was among the first to congratulate the couple.
Former US first lady Michelle Obama - who memorably met Prince William's first born son George - said she and Barack Obama "can't wait" to meet Harry's boy.
Prime Minister Theresa May led the political congratulations, while her Home Secretary Sajid Javid clarified his own position on the birth.
Home Secretaries used to be present at the births of royals to ensure the new arrival was a genuine descendant of the monarch and had not an imposter smuggled in.
However, the last time this happened was in 1936 for the birth of the Queen's cousin, Princess Alexandra.
Then Home Secretary Sir William Joynson-Hicks was present at the Queen's birth in 1926.
Why is much of the news of the birth private?
Speaking on Monday, Prince Harry said he and Meghan plan to celebrate the new arrival privately before revealing their new son to the public in a couple of day's time.
It means the Sussexes will not follow in the footsteps of the Duke and Duchess of Cambridge and present the new arrival to the public just hours after the birth.
How and where were other royal babies introduced to the public?
Prince George, Princess Charlotte and Prince Louis all made their first public appearances on the steps of the Lindo wing.
The Duke and Duchess of Cambridge introduced their three children to a bank of photographers and cameras outside St Mary’s Hospital in Paddington, London.
Where was the new baby born?
The Duke and Duchess of Sussex's baby plans reportedly saw a late change when Meghan was taken to a London hospital to give birth.
The as-yet-unnamed infant was believed to have been born in the sanctuary of Frogmore Cottage - the Sussexes' home on the Windsor Estate.
But the Daily Mail reported that Meghan had her son at a London hospital, possibly The Portland.
By opting for the private hospital on Great Portland Street, Meghan and Harry would have departed from recent precedent set by the Duke and Duchess of Cambridge, whose children were all born at St Mary's Hospital in Paddington.
What have the celebrations been like?
Royal fans descended on Windsor to uncork the bubbly and soak up the celebratory atmosphere after the birth was announced.
Royal babies are also usually commemorated with gun salutes in Green Park or Hyde Park and at the Tower of London.
But it is not yet known whether Harry and Meghan's boy will be accorded the tradition.
Who could the godparents be?
Tradition dictates that the godparents of the newborn bab will be announced on the morning of his christening in a few months' time.
However tradition may no be observed in this royal birth, as we have seen on multiple occasions already.
Among the famous names leading the way are Amal and George Clooney, Serena WIlliams and Oprah Winfrey.