PRINCE William was reportedly left seething after a suggestion that Catherine, Princess of Wales, should tweak the spelling of her name for royal branding reasons.

In royal author Christopher Andersen’s book, “Kate! The Courage, Grace, and Power of the Woman Who Will Be Queen,” he writes that King Charles III and Queen Camilla were concerned about having “too many C’s” tied to royal monograms. Andersen says Charles and Camilla already had royal cyphers featuring interlocking C’s beneath a crown, and worried another C-based cypher was “overkill.”

Andersen claims the proposal was that Catherine change her full name spelling from “Catherine” to “Katherine.” He writes that William responded on his wife’s behalf, calling the request “insulting” — not just to Catherine, but to the Middleton family.

Andersen argues the episode shows how seriously the royal household takes image and branding, down to “the letters in their crests and coats of arms.” He also says William has defended Catherine since early in their relationship, and cites his reaction after topless photos of her sunbathing were published in France in 2012, claiming William pushed for legal action under French privacy laws.

He adds that Catherine prefers to be known as Catherine and feels strongly about the name given to her by her parents, even though the world widely knows her as “Kate.” Andersen writes she is “genuinely fond” of Charles and didn’t hold ill will over the idea, later noting the couple’s “simultaneous cancer diagnoses” put other matters into perspective.

Others quoted dismiss the alleged request as a dead end. British broadcaster and photographer Helena Chard calls it a “nonstarter,” suggesting Charles and Camilla were approaching it with a “business head,” while royal broadcaster Ian Pelham Turner describes it as a potentially “volatile moment” as she joined the family. Royal expert Richard Fitzwilliams is blunter, saying: “If true, it’s idiotic.”

A Kensington Palace spokesperson said there would be no comment on books.