The Queen promised Lois, 6, and Harriet, 10, that she would transport their letters “carefully” for the Princess, responding to Harriet’s apology that the cards, drawn on Tuesday, had become “a bit creased” in the wind.
“I’ll take them carefully and will make sure she knows they’re coming,” the Queen told the two girls.
Speaking afterwards, Harriet said: “We heard the news and I wanted to hold the poster up to show my love to Kate.”
Lucy Waterston, their mother, who did not think the Queen would even get to see the cards, said: “She said she certainly will send her love.”
The well wishes come after the Princess revealed in a personal video message last week that she is currently receiving the “early stages” of preventative chemotherapy.
Another well-wisher sent their “best wishes to His Majesty”, to which the Queen responded “thank you”. She also thanked a woman who said she was thinking of her during this time.
Speaking after she left, Joanne Morris, 65, said: “She’s got a lot on and it’s a big thing – you think it’s an easy job, but it must be very, very tiring.”
More than 2000 people came to catch a glimpse of the Queen during her first engagement meeting the public since the Princess’s announcement.