A dressed down Kate reportedly kept a low-profile in a brown gingham dress she's worn on previous occasions, pumps and black sunglasses.
According to Vanity Fair, the royal trio were accompanied by the family's longtime nanny Maria Borrallo and three protection officers.
Vanity Fair claims that Princess Charlotte was having so much fun on the family walk, she was hesitant when mum told her it was time to go!
Over the years, Kate and the kids have often been spotted strolling around the public grounds of Kensington Palace which are outside their 1A apartment.
Kate is expected to make her first public appearance since welcoming her third child this Saturday, and while Prince Louis is far too young to attend the royal affair, siblings Prince George and Princess Charlotte have been announced as members of the bridal party.
It's believed the next time we'll see Prince Louis will be at his christening, which will likely happen in the coming months.