He got his wish! Brits and anglophiles all across the world are celebrating England's new royal baby princess Charlotte Elizabeth Diana — but no one more than her proud daddy! Outside St. Mary's Hospital in Padddington, London, Us Weekly's European Bureau Chief Omid Scobie got an inside look at Kate Middleton and Prince William's newly expanded family of four with the help of royal expert Katie Nicholl.

According to the Kate: The Future Queen author, the Duke of Cambridge has been anxiously hoping for a daughter. "I know Prince William will be absolutely delighted," Nicholl told Us. "He has secretly wanted a little girl. He wanted a girl [since] Prince George's [birth]. And I think it's wonderful. Now they have one of each."

Indeed, and Prince George's little sister is now the fourth in line for the British throne. "This will be the first princess for Cambridge for about 180 years," Nicholl noted. "There's a real historical significance to this baby."

As previously reported, Middleton gave birth to the bundle of joy at 8:34 a.m., just a few hours after going into labor. The turnaround was so quick, in fact, that Nicholl believes she must have stayed at Kensington Palace until the last possible moment.

"This was a very quick birth," she told Us. "When you have a second baby I think you are a bit more relaxed and you let those contractions go a little bit longer."

As for whether they truly didn't know the sex of the baby? "They like to keep a secret and they know how to keep a secret," she mused. "You wonder if perhaps they did know — or perhaps a happy coincidence!"

Up next, Middleton and Prince William will head back to Kensington Palace with their children before traveling to their Amner, Norfolk home.

"I don't think we will be seeing them for a while [after]," Nicholl explained. Following the princess' debut outside St. Mary's, Nicholl predicts that the next time the world will see the foursome will be during the baby's christening in either September or October.

For more on the royal couple's life in the countryside and their new baby girl, watch the video above!

Us Weekly is on the scene outside St. Mary’s Hospital in London — check out the exclusive livestream and check back often for ongoing updates on all things royal baby!