Was ever a damsel more beset by hissing dragons than England's Princess Margaret? Three controversial books—Willi Frischauer's Margaret, Princess without a Cause, Simon Regan's Margaret, a Love Story and James Brough's Margaret, the Tragic Princess—tell lurid tales of the 47-year-old Margaret's emotional problems, her declining beauty, her separation from Antony Armstrong-Jones and her liaison with 30-year-old Roddy Llewellyn. Brough even attributes Margaret's sad history to an inherited "royal malady"—porphyria, the metabolic disorder that made King George III appear to be mad.

While the princess enjoyed a respite last week, traveling to the U.S. to attend a benefit ball (her nephew Prince Charles was also touring here), a most unlikely Saint George arose back home to defend her. He is Nigel Dempster, the Daily Mail's gossip columnist. In just four years Dempster's scoops on upper-crust lecheries and lagniappes have made his Daily Mail "Diary" what he modestly calls "the most written-about column in the Western world." Dempster hates the "inaccuracies" printed about Margaret.

"Margaret," Dempster says, "is an unfortunate member who is extraneous to the royal family, especially now that the younger ones are coming up." He's written a three part defense for a British magazine, and promises to follow up with a book about the princess and her family. Other members of the royal household may find that his avenging sword has a double edge—especially the men, about whom Dempster does not hold his tongue.

"Prince Charles," the columnist notes, "brings a pretty girl onto the polo field in front of 20 cameramen as a shield to hide his real affairs with married women."

"The Duke of Edinburgh has had a long and ongoing friendship with a titled lady."

"Tony Armstrong-Jones is ambitious, a glorified hustler. He talked Margaret into marrying him. It gave him a great deal of pleasure to have the two children."

Claims the dapper Dempster over champagne (his tipple) and smoked salmon at his Berkeley Square club: "I have expanded the horizons of personality journalism. I write only about actions in public. One should not listen at keyholes. People make the mistake of flaunting their money and behavior. Then when things go wrong for them, they don't want it to be known."

Born 37 years ago in Calcutta to a well-to-do Australian businessman, Dempster came to England at 4. "I was always hated by my parents," he says. "I was delighted to leave them." Departing a posh private school at 16, he took a series of motley jobs. Then at 20 he became assistant to the Earl of Kimberley and an informant for gossip columnists. Dempster says he attended some 800 deb dances and 1,500 deb parties during the next seven years, stockpiling his prodigious memory with the names, faces and closet skeletons of—by his own count—3,000 aristocrats. "I write about the misfortunes of the privileged so the masses will realize they are no less unhappy."

Aided by a staff of four, the tireless Dempster puts in 14-hour workdays that begin with a 7 a.m. jog and squash game. He also writes for other British publications and does TV and radio interviews. "I want to succeed," he explains.

Despite two titled wives (his three-year marriage to Swiss Countess Emma de Bendern was ended by divorce in 1974), Dempster disclaims social ambitions. "I'm just a colonial," he says. "I don't try to mix with titled people." But he attends an occasional do with his bride of four months, the wealthy Lady Camilla Harris.

Although Dempster has been on the losing end of two recent libel suits, he manages the last word: "You can't be a journalist unless someone is afraid of you. You must establish yourself as a man of power, though it is ephemeral power. The most we do is ruin someone's breakfast."