As knife crime grips the nation's inner cities, and gangs run amok on council estates across the country, a shocking new report has revealed how teen violence is now spreading to other social demographics.
Square-jawed, ruddy-faced groups of youths in Barbour jackets and green wellies are terrorising debutante balls and farmers' markets, with more than half carrying concealed muskets and other antiquated firearms.
One toff, a former member of the notorious Henley-on-Thames-based Blue Blood Boyz, said turf warfare and feudal disputes were rife. Tarquin (not his real name) wears an eye-patch after being slashed with a fencing foil for "disrespecting" a rival's mother. Now he has quit the gang scene for good - and wants to help others do the same.
"Kids do it just to fit in. It's peer pressure," Tarquin said. "Actually, in the case of my old leader Hugo Delaney, the 3rd Marquis of Dorset, it really IS Peer pressure."
"And it's spiralling out of control. One minute you're only involved in some low-level joshing about the Montague family's plebeian ancestors, and before you know it, Bam! Toby Featherstone-Prigg is killed in an illicit jousting match - lanced through the heart in an act of cruel retribution and splendid pageantry."
Branding the flesh of new members with gang "colours" (usually a pithy Latin dictum or coat of arms) is another terrifying hallmark of this brutal epidemic. Well-to-do fops as young as twelve are habitually mutilated with red hot pokers in horrific initiation ceremonies in the dormitories of Harrow and Eton - key recruiting grounds for the aristo-gangs.
In days gone by, public school "fag" duties used to involve innocent toilet-seat warming and wedgies at the hands of charming, roguish prefects. But they are now altogether more sinister, with younger boys required to run guns in and out of the boarding house and smuggle crack cocaine into parties at Windsor Castle without being pinched for ransacking Prince Andrew's private stash.
Tarquin is glad to be out, but acknowledges his future safety can never be assured: "I'll always be looking over my shoulder," he continued. "Most of the Harry and Wills set inside Movida and Boujis are carrying. If you accidentally knock over the wrong glass of Cristal, you'll be instantly slapped with a silk handkerchief and challenged to pistols at dawn - no questions asked."
The authorities have long turned a blind eye to this toff-on-toff hostility - but with Hunt Ball happy-slappings and arson on luxury yachts at an all-time high, they have been forced to act. Police announced a weapons armistice at the recent Cartier Polo event and retrieved an astonishing haul of items, with contraband including several diamond-encrusted bodkins, a couple of high-velocity hunting rifles, and a full suit of armour from the Battle of Agincourt.