First, let’s get this straight: It’s Catherine with a C, not Kate with a K.

That’s how the young woman who becomes HRH Princess William of Wales on Friday prefers to be addressed.

Which tells you something about her style even if you haven’t joined the throngs already dissecting her outfits or rushing to copy them: She’s a proper sort.

Her fashion aesthetic, if you need a label, leans toward what Huffington Post’s royal expert, Yvonne Yorke, calls “modern Sloane Ranger.” William’s mother, the late Princess Diana, was an archetypal Sloane Ranger when she joined Great Britain’s royal family in the early 1980s.

It’s essentially Brit prep, with key pieces such as fitted blazers, riding boots, country tweeds and discreet jewelry, worn with a fresh face and glossy hair.

Fashion insiders who think royal closets should be more creative — including the wildly colorful British designer Vivienne Westwood — have suggested Middleton dresses too conservatively.

Houston-based public relations executive Maggi Jones, who’s from Great Britain, also finds Middleton’s style “achingly appropriate.”

“She’s wearing the uniform,” Jones noted. “She’s a perfect clotheshorse — tall, thin, with beautiful skin and wonderful hair. I’m sure she’s not wanting to stand out or draw bad media, but I hope she’ll be more adventurous later. She could revitalize the U.K. fashion industry.”

Yorke, who last weekend identified little-known British designer Sophie Cranston as the likely designer of Middleton’s wedding gown, likes what she sees.

“Catherine has, in general, quite classic tastes which will serve her well as a member of the royal family,” Yorke said in a phone interview. “You don’t want to be looking back at photos in 10 or 20 years and going, ‘What was I thinking?’ So it’s good that she stays away from overly trendy styles.

“Looking ladylike never goes out of style. The key for any royal is to dress appropriately for the event, not be a fashion trend-setter.”