For many, it's among the most famous pictures of the Camelot era: former President John F. Kennedy working at the famous HMS Resolute desk in the Oval Office as two-and-a-half-year-old John Jr. peeks out from a secret door in the front.

Snapped by Stanley Tretick just a month before JFK was assassinated in Dallas in 1963, it was a photo shoot opposed by former first lady Jacqueline Kennedy but secretly cheered by the president who waited for his wife to leave town to give the photographer the green light, according to an engaging new picture book about Tretick's private cache of Kennedy photos, memorabilia and personal stories.

Written by Tretick's friend, celebrity author Kitty Kelley, "Capturing Camelot: Stanley Tretick's Iconic Images of the Kennedys," reveals new details of the Oval Office photo shoot. According to Kelley, who was given Tretick's secret JFK stash after he died in 1999, the photographer had been begging for a father-son photo shoot after a family portrait on the cover of Look magazine sold out.

His lucky break came in October 1963 when Jackie, grieving over the death of prematurely born Patrick, traveled to Greece to vacation on the yacht of Aristotle Onassis, who she would later marry.

In the new book, provided to Secrets, Kelley writes: "'Just as soon as Jackie left town I got the call that the coast was clear,' Stanley recalled, 'and I hightailed it to the White House.... When the president saw me, he said, Now, you know we better get this out of the way pretty quick. Things kind of get sticky when Jackie's around.'"

At 7 p.m., Tretick, portrayed by Kelley as the semi-official Kennedy family photographer, waited outside the Oval Office until nanny Maud Shaw arrived with John Jr. in pajamas and a robe. Upon entering the Oval, the boy cheered, "I'm going to my secret house," writes Kelley.

At least twice, John Jr. scampered under his dad's legs and out the desk door, giving Tretick a series of unforgettable pictures. Even JFK knew they were gold, telling Tretick, "You can't miss with these, can you, Stan?"