Prince William was in a great mood during the royal wedding reception.

Prince William and Kate Middleton attended Prince Harry and Meghan Markle's royal wedding on Saturday. According to an insider, the Duke and Duchess of Cambridge let loose during the private evening reception.

"William was in a jokey, wonderful mood at the party," a royal wedding guest said. "He must have been relieved that it wasn't all about him."

The insider added that Prince William was very pleased to see his brother happy. "He is so proud of his brother," the source said.

Prince William and Middleton were also very glad that Prince George and Princess Charlotte were part of the nuptials.

"She was [in] great form," a wedding guest said about Middleton. "She and William were saying how thrilled they were to have their children there taking part."

Prince George and Princess Charlotte were visibly enjoying the event. In fact, they were grinning in the official royal photos. According to the royal wedding photographer, the children were bribed with candies.

"Who likes Smarties?" Alexi Lubomirski revealed the trick they used to make the page boys and bridesmaids smile in the portrait in an interview with Reuters (via Town & Country). "They were being bribed with one Smartie here, one Smartie there, so as soon as the kids came onto the set, I immediately just shouted out 'Who likes Smarties?' and then everybody, hands up, smiles, even some adults put their hands up."

He also added that some of the children's parents, uncles and aunts talk to them to behave appropriately during the photo shoot. "It was a family, that was essentially what it is," he explained.

Meanwhile, on Tuesday, Markle made her first engagement as an official royal at Prince Charles' garden party. She arrived with Prince Harry. But Prince William and Middleton were both missing.

Prince William didn't make it to Markle's first engagement as an official royal because he was in Manchester Cathedral to mark the first anniversary of the Manchester Arena attack. Meanwhile, Middleton missed it because she's still on maternity leave.

"It is traditional for new royal mums to take a six-month break from official engagements," Duncan Larcombe told Harper's Bazaar. "The wedding doesn't count because it was a 'family affair' but other than that, she will pick and choose her engagements. If she wanted, Kate could disappear into the background until October!"

Prince William and Meghan Markle
Prince William and Kate Middleton missed Meghan Markle's royal debut at Prince Charles' garden party. Pictured: Prince William, Camilla, Middleton and Prince Andrew attend the wedding of Prince Harry to Meghan Markle at St George's Chapel at Windsor Castle on May 19, 2018 in Windsor, England. Getty Images/Jonathan Brady