Prince Charles declared the newborn tot was "perfect" and "marvellous" after slipping into the Lindo Wing with his wife Camilla to congratulate William and Kate.
Asked about his first grandchild, the elated royal sent the crowd into rapture as he confirmed the couple would pose on the steps - just as he and Princess Diana did 31 years earlier. Talking of the 8lb 6oz prince, Charles said: "He's marvellous, thank you very much, absolutely wonderful - you wait and see, you'll see in a minute."
In a break from royal protocol, the first visitors to the top-notch maternity unit were Kate's parents, Michael and Carole Middleton.
Their trip to the Lindo Wing is the strongest hint yet that the baby will enjoy a far more normal upbringing than Wills and his brother Harry, 28.
Carole admitted she was overcome with emotion at being the first family member to meet the little lad.
Looking summery in a blue polkadot dress similar to the one her daughter wore later in the day, she gushed: "He's absolutely beautiful!" The pair spent just over an hour admiring their grandson inside the central London maternity ward.
And on the subject of whether or not they had suggested a name, she laughed and said: "Absolutely not."
Kate, 31, is now expected to stay with her parents at their home in Bucklebury, Berks, where they will help her cope with the challenge of looking after a new baby.
Salute Earlier in the day Camilla, Duchess of Cornwall, said she believes husband Charles will make an exceptional grandfather.
During a series of engagements in Yorkshire, Camilla said: "I think it's wonderful news. I think mother, son and father are all well.
"And I think it's a wonderfully uplifting moment for the country.
"It's very exciting and it's wonderful for the grandfather - he's brilliant with children."
Meanwhile, Brits welcomed the new addition to the Royal Family with mass celebrations.
In Kate's home village, champagne corks were popping and villagers cracked out the bunting.
Crowds were also visible throughout the night outside Buckingham Palace, where the notice of the little boy's birth was posted.
Later in the day the Band of the Scots Guards performed Cliff Richard's hit Congratulations following the Changing the Guard ceremony - joined by some of the hundreds of well-wishers who sang along.
The King's Troop also staged a 41 royal gun salute in Green Park watched by tourists.