The star told her family that she had simply headed off on a well earned holiday with her Australian boyfriend Ryan Clark.
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But HELLO! can reveal they actually wed at the famous Little Church of the West in Las Vegas.
"I love going to other people's weddings but I have never desired a big white wedding for myself and it has never been put on me as a pressure, an expectation," says Barnsley-born Katherine who married 33-year-old Ryan, a digital analyst manager, on August 20th.
"The day was everything we hoped it would be - no fuss, low key, sunshine and just us!" 33-year-old former Corrie star Katherine exclusively told HELLO!.
"We wanted to enjoy the day without all the usual planning and pressure. We just wanted to let it roll, so it had an on-the-run feel to it," she said.
"We'd been laughing and joking all day and then suddenly, everything seemed to stop and we tried to get the words "I do" out without becoming emotional wrecks. It was awesome. I'll never forget that moment for the rest of my life."
And, explaining why she wanted to become a runaway bride and not tell her family of the nuptial, she told HELLO!: "Selfishly, I just wanted Ryan to myself that day. So many people say you have to remember to grab hold of your bride or groom and spend time with them. I think if we had done a traditional wedding we would have been doing it for everyone else but this was about the two of us."
For the full wedding album and interview see the new issue of HELLO! on sale now.