EXCLUSIVE: Princess Diana and JFK Jr. – The Lies, Lust and Shocking Offer at Heart of Pair's Secret Bond

Princess Diana had an ulterior motive. Though she accepted John F. Kennedy Jr.'s invitation to meet up at NYC's Carlyle Hotel and discuss a potential work collaboration, the newly single royal already knew she was going to pass on the opportunity. Instead, Di wanted to get to know America's Prince on a more intimate level, RadarOnline.com can reveal.

The 1995 after rendezvous took place in the Carlyle Hotel and before 1995 after JFK Jr. reached out to the People's Princess in a personal letter.

"Nobody wanted it to be public," Diana's private secretary, Patrick Jephson, said in JFK Jr.: An Intimate Biography by Liz McNeil and RoseMarie Terenzio, who was Jephson and John's assistant. "It was never made public, so that made it quite fun, actually."

Now, RadarOnline.com can reveal shocking new details about the clandestine encounter from the sordid lies that drove Di toward JFK Jr. to her physical attribute that had the political scion drooling. Two of the most prominent figures of the '90s, "it had all the makings of a great gossip story," said Jephson.

"World's most eligible bachelor, wasn't he at the time? And she had just got unmarried or was in the process of getting unmarried."

Indeed, Di separated from Prince Charles in 1992 – and had given a bombshell interview about the crumbling of their marriage weeks before connecting with JFK Jr. Intentionally keeping the palace in the dark ahead of her BBC tell-all, she spoke of the future king's longtime affair with Camilla Parker Bowles, who, of course, is now wed to the monarch.

For the first time, Di also admitted to stepping out on her royal union, herself enjoying a five-year liaison with riding instructor James Hewitt. "Yes, I adored him," she said. "Yes, I was in love with him."

While Prince William would later condemn the TV sit-down as exploitative, his mother was seemingly feeling emboldened when she received JFK Jr.'s invite. But they needed help to pull the covert meeting off. So the duo enlisted RoseMarie to coordinate sneaking the businessman into Diana's penthouse suite.

Once there, JFK Jr. – who'd become obsessed – tried hard to court Di for the cover of his recently launched magazine, George. However, the princess, who'd given birth to future king William, now 44, 13 years earlier, appeared more interested in how JFK Jr. navigated the intense media scrutiny they'd faced since childhood.

"I'm hoping he'll grow up to be as smart about it as John Kennedy Jr.," she told The New Yorker's Tina Brown of her little boy in June 1997. "I want William to be able to handle things as well as John does."

According to Jephson, there was also a "flirtatious" element to the encounter. He alleged Diana sat down with hunk JFK Jr., in part, to make sister-in-law Sarah Ferguson jealous. Still, Jephson insists Di "didn't see him as the rest of the world saw him. As this big, famous, handsome guy. She saw him, I think, as rather vulnerable."

Despite Diana turning down his magazine offer during their 90-minute get-together, JFK Jr. was left with a positive impression too, reportedly calling the blond beauty "lovely" and "demure" to close confidantes.

In The Kennedys and the Windsors, author Caroline Hallemann reports the editor-in-chief also gave his staffers a rundown of the special encounter. "Well, she said no," John allegedly recalled. "But she had a great pair of legs."

Sources said now-77-year-old Charles, who finalized his divorce from Di in 1996, didn't know much about her hush-hush interaction with the American heartthrob and didn't care to know. It's perhaps surprising considering the communication between the twosome didn't stop after their meetup.

Per JFK Jr.'s assistant RoseMarie, he and Kensington Palace-based Di continued to "stay in touch," exchanging letters back and forth.

Therefore, it was all the more heartbreaking when the princess died in a Paris car crash in August 1997 at the age of 36.

As pal Steven M. Gillon recalled it, JFK Jr. "had an emotional reaction" to Diana's death, which came as she was being hunted down by paparazzi.

His spouse, Carolyn Bessette Kennedy, did as well. Married to JFK Jr. the year before, the former Calvin Klein employee had apparently grown paranoid about all of the media attention she was receiving. "I think he thought, 'This is going to push my wife over the edge even now,'" RoseMarie dished of Diana's tragic passing.