A 6-year-old girl is celebrating Christmas in July after cancer forced her to miss the festivities last December.

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Agatha King, 6, was one of 20 children invited to the holiday-themed celebrations in London, England, earlier this month, where they took turns riding sleighs, playing in the snow and meeting Santa Claus.

“We colored in pictures of the snow globes. There were games, too, and sweets,” Agatha told InsideEdition.com. “I felt really excited.”

Her mom, Karen King, said Agatha was diagnosed with acute lymphoblastic leukemia when she was 4. Her compromised immune system means that her family, including her brother Bacchus, now 4, and 1-year-old sister Meredith, needs to be careful of where they go.

“You miss out on all of the things to build up to Christmas – parties, switching of the lights in the town, ice skating,” King explained. “Nobody ever expects childhood cancer to enter our lives. It’s something we never considered.”

Last winter, Agatha was in and out of the hospital and was too ill to participate in the holiday fun, including a nativity play at her school, even though she had been rehearsing for months.

But thanks to Cancer Research UK, several childhood patients were able to enjoy the winter celebrations at the Christmas party held at Two Temple Place.

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“Lots of tears were shed because it’s so nice to see them being well enough to enjoy things,” Agatha’s mother said. “It’s lovely to be with other families. They just get it, they understand what you’re going through.”

Despite the diagnosis, King said Agatha has been mostly in good spirits.

“Agatha’s probably kept us all going,” her mom said. “She takes everything in her stride. Her energy gives us energy and keeps us going.”

Watch: Dad Fights to Keep Cancer-Stricken Wife Alive So She Can Watch Their Son Open Christmas Gifts