Unplanned visits, chance meetings, impromptu drinks--these are just the sort of Filofax-be-damned encounters royal life does not amply provide. On a Friday evening last month, however, at Prince Charles' St. James's Palace apartment, there occurred some rather significant spur-of-the-moment socializing. Just nine days before his 16th birthday, Prince William, en route from boarding school to the movies with friends, called his father to tell him he'd be stopping home for a change of clothes. Prince Charles asked his son if he would not mind spending a few moments with a houseguest, one the boy had never met before--Charles' mistress of 26 years, Camilla Parker Bowles.

Anxious, Parker Bowles, the 51-year-old divorce who helped break up the Prince's marriage to Diana, offered to exit. But Charles encouraged her to stay; Wills was looking forward to an introduction. When the teenager arrived, the threesome spent half an hour sipping tea and soft drinks. After Wills left, Parker Bowles reportedly asked for a vodka tonic to calm her nerves. The encounter went smoothly though, and the young Prince has since sat down with Parker Bowles twice, once alone for tea and later for lunch with his father. If he is amenable, Wills' brother Harry, 13, might soon meet Parker Bowles.

News of the get-togethers appeared with much fanfare in the British press last week. Initially reported by the Sun, the story was confirmed by royal-family spokesmen who leveled no objections to its publication. The palace's surprising compliance immediately sparked questions about whether there is a movement afoot to introduce Charles' frequently maligned paramour into public life.

Their relationship had become less closeted in the months before Diana's death last August. But in the wake of that tragedy, the woman Diana once deemed "the Rottweiler" again retreated from view. By March, however, tabloids had got wind that Parker Bowles was spending nights at St. James's as well as the Queen's Sandringham estate. More recently, Parker Bowles has begun to emerge on the social scene. Just a few weeks ago, she attended a gathering thrown by Charles for prominent members of the Greek community at his country place, Highgrove. Last month she turned up at Sir David Frost's annual garden party in London.

Speculation about who exactly might have leaked news of the Wills-Camilla meeting has turned into something of a London parlor game. The palace was furious at the suggestion that it provided the tip-off. Indeed, Prince Charles was said to be upset that word had filtered out; he surely understood that Diana's friends and fans would find it insensitive to have Parker Bowles meeting Wills before the first anniversary of the princess's death. Another theory has it that friends of Parker Bowles passed on the information in hopes that it would help redeem her reputation among the citizenry.

Should Parker Bowles ever gain the acceptance her friends wish for her, it is still unlikely that she and Charles would wed. The couple, according to royal watchers, has accepted the fact that marriage is not an option. Charles hasn't intimated that he would forfeit the throne to make Camilla his wife. The most they can hope for is a comfortable live-in relationship.

And for that reason alone it makes sense that Parker Bowles should involve herself in the lives of the young princes. Says Harold Brooks-Baker, publishing director of Burke's Peerage: "The situation has been ridiculous. Camilla and her ex-husband are courtiers and socially part of the royal circles whose paths cross all the time. The princes must be the only children in the whole royal group who don't see her." Now, it seems, they'll have countless chances.

--Reported by Helen Gibson /London