“They are paralyzed,” said Mario Daneels, a Belgian writer who first revealed in a book published in 1999 that Albert fathered an illegitimate child in 1968 with his mistress then, a Belgian aristocrat. “They don’t know what to do. You put a camera in front of a Belgian royal and they start stuttering.”

Ms. Boël, who says she is that child, has steadily escalated what began as a discreet lobbying campaign for recognition into a very public battle to break down the palace’s defenses. A professional artist, she has turned art into an irreverent weapon. A neon sculpture she created reads “Love Child,” the two words separated by a red heart topped by a yellow crown.

In a series of interviews with Belgian and French news media, Ms. Boël has insisted that she has no claim on the king’s fortune, but simply wants to heal the wounds caused by decades of rejection. “I am deeply saddened, but I believe blood can work wonders,” she was quoted as saying last month after she began a legal action to try to prove her royal lineage through DNA tests.

Complaining of canceled bank accounts and other indignities because of “the situation surrounding my existence,” Ms. Boël said in a statement, “I don’t believe that my legal action will end all discrimination against me or my family, or mend my personal relationship with my father, but with DNA proof there will be undeniable certainty about my identity.”

Albert II, a genial figure who mixes easily with his subjects, has worked hard during his 20-year reign to narrow the gulf between his country’s Dutch-speaking regions in the north and Francophone areas in the south. Many Dutch speakers still view the monarchy as an alien institution that speaks mainly for the French-speaking community, but few bear Albert any personal animus. His son Philippe speaks Dutch as well as French but has a more prickly and rigid character that will make mediation even more difficult.

Across the linguistic divide, reverence and even respect for the monarchy have become increasingly rare. The news media in both languages now jump on royal gaffes and any hint of scandal. “I almost feel sorry for them,” said Mr. Daneels, the writer. “There is a climate where they can’t do anything right.”