Like other Washington fashionistas, I eagerly anticipated seeing what Kate Middleton, now the Duchess of Cambridge, would wear to her wedding, now that she finally had her man. The identity of the designer had been kept with Situation Room-like secrecy. Rumors abounded that Sarah Burton, the shy and unflamboyant heir to the late and lamented Alexander McQueen, had created the dress. But could it be another of Britain’s of-the-moment designers?

I doubted that Kate would end up enveloped in a meringue confection the way her should-have-been mother-in-law had been. Perhaps she would pick something fashion-forward and edgy. Something to show that Britain’s royals had moved into the 21st century?

Glued to the television early Friday morning, I watched as she emerged from her hotel and tucked herself into the car waiting to whisk her to Westminster Abbey. The camera zoomed in, straining to catch details of the dress, the train, the veil. As it became easier to see, commentators instantly and unanimously declared the dress a success. So modern, yet classic and romantic. The perfect choice.

But I was stunned. Kate was wearing an exact replica of the wedding dress I had worn — and I was about to celebrate my 20th anniversary! A dress I had picked up in 1991 at Kleinfeld’s in Brooklyn, off the rack and on sale (albeit in the high-end department).

I grabbed my wedding photos and showed them to anyone who would look. Yes, they gasped, it was the same lace bodice with the plunging neckline, the slight collar, the bustle in the back anchored by buttons. No, my lace hadn’t been specially designed for me, and my train was considerably shorter. But the cut and design were almost identical.

Clare Cushman and her husband Amedee Prouvost at their 1991 wedding. (Courtesy of Clare Cushman)

Friends who attended my wedding started calling and e-mailing, asking whether their memories of my dress were right. My mother called ship-to-shore from a cruise in Greece. Waity Katie stole your dress! Even my 16-year-old daughter, an aspiring costume designer, noticed the similarity and excitedly texted me while she was on a break from school.

As The Post’s Style editor and other fashion commentators weighed in again and again over the next few days, I wanted to scream. Yes, Kate looked beautiful and regal in her dress. Even I had felt like a princess wearing it. But was it original? No! Maybe nothing in fashion ever is.

My husband sweetly said that if People magazine ran its “Who Wore It Best?” feature, I would win. (Note to William: That’s how you get to 20 years of marriage.) But I think he was more excited by the fact that he still has more hair than the groom.