The Duchess of Cambridge revealed that her son, Prince Louis, was "bombing" around on his walker: "Louis just wants to pull himself up all the time. He has got these little walkers and is bombing around in them."
The 37-year-old sympathised with one little bub who started to cry: "There's so many people here,” said Kate.
The mum-of-three look effortlessly chic in a purple Gucci blouse and Jigsaw pants.
Middleton has previously discussed the importance of supporting kids' mental health.
"The mental health of our children must be seen as every bit as important as their physical health,” she wrote in a personal essay for Huffington Post UK.
"For too long we have been embarrassed to admit when our children need emotional or psychiatric help, worried that the stigma associated with these problems would be detrimental to their futures."
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