The Royals

Queen Elizabeth Loves to Laugh with Her Grandkids

By Simon Perry

05/25/2012 at 07:45 AM EDT

Queen Elizabeth Diamond Jubilee: Her Grandkids Speak Out

Princess Eugenie (left) and Queen Elizabeth

Andrew Milligan - WPA Pool/Getty

To the outside world, Queen Elizabeth sometimes appears as a poker-faced woman who seldom lets down her guard or offers up an opinion.

But when she's around her eight grandchildren (and two great-granddaughters), she "lights up," according to one of them.

Princess Eugenie, 21, says she loves telling the 86-year-old monarch about life at university. "We talk about my Newcastle life and how I've got so many essays and things and she still goes, 'Aha,' [and] laughs at what I say, which is lovely," Eugenie says during an ITV1 special, Elizabeth: Queen, Wife, Mother, airing in Britain on June 1.

PHOTOS: Celebrating Queen Elizabeth's 60-Year Reign

When Eugenie was younger, "Granny would take us raspberry picking, and we'd have the raspberry jam that we picked that day on the table for tea," she says.

Eugenie's cousin, Prince William, 29, adds that the Queen and husband Prince Philip, 90, are good at seeing the funny side when things go awry at formal events. "The Queen has seen so many parades or performances when there's a small slip-up it tickles her humor."

Like her sister Princess Beatrice, Eugenie lives at Royal Lodge, where the Queen grew up. "When she comes back here she remembers her childhood," says Eugenie, who is sensitive to how it must remind her grandmother of her late sister, Princess Margaret.

"It must be so sad not to have Margaret around any more," says Eugenie. "I'm sure she's looking down, very proud of her sister."

PHOTOS: Queen Elizabeth II: 60 Years of Style