Kate Middleton made a rare appearance in a London park to spend quality time with Prince George. The mother and son were spotted in Holland Park on Sunday.

The picturesque park is just a 10-minute drive from the royal family's residence at Kensington Palace.  An eyewitness at the west London park told Hello! that Kate and George were in the park’s play area at 10 a.m. "They were running around on the rides, the swings, roundabouts and slides. They were on their own, just them two."   

The Duchess of Cambridge was very playful as she pretended to be a monster, flailing her arms about while chasing Prince George. "She was play-acting, just like all mums do, and he was running around loving it -- he looked very happy," an onlooker told People.  

George clearly enjoyed having his mom all to himself. Prince William wasn’t with them since he went to a charity polo match on Sunday and Princess Charlotte was nowhere to be seen. An onlooker even shared that George was such a happy lad, being chased by his mom and enjoying all the rides. “They looked just like any other mom and toddler."

While Kate and her son George had a low-key play date, men who appeared to be royal security guards requested that onlookers not take pictures. Although one eyewitness just couldn’t resist sharing the news with his Twitter followers, writing: "Saw Kate and George at Holland Park today. Security guys were also understanding and let us continue shooting our photos :)."

According to Hello!, royal watchers are speculating that Kate and George will stay in London to make an appearance at "Trooping the Color" -- Queen Elizabeth II’s birthday parade, which will take place June 13. This will be the Duchess’ first public appearance since giving birth to Princess Charlotte on May 2.

Meanwhile, William and Kate’s London home will be very busy in the coming months. Nicky Hilton and James Rothschild will be having their wedding at Kensington Palace on July 10, reported Page Six earlier this week.

The American hotel heiress and her British bank heir fiancé will be tying the knot at the Orangery within Kensington Gardens. The Orangery is licensed for civil weddings and allows receptions on its terrace. It is also located next door to William and Kate's apartment.