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Liberty, 33, an aristocratic beauty in the mould of Jasmine Guiness or Stella Tennant, met Rupert when she 17.
Of the early days of their romance, she said: "'Once we started going out, I knew he was the one for me. He is a very special soul."
What Kristen described as an "indiscretion" was probably even harder to comprehend because Liberty herself also appeared in Snow White And The Huntsman as the starlet's mother and had championed her casting.
Ironically, a few weeks ago the English rose hinted that she and Rupert, 41, had gone through difficulties in their marriage and appeared to think the troubles were behind them.
Liberty, whose grandfather was Lord Killearn, told YOU magazine that moving from London to LA had been quite an adjustment.
"I think that having been a model and so self-sufficient for those years, I was very ready to get married and have babies.
"I romanticised domesticity for a while, and loved having a shopping list of groceries stuck to the fridge for the first time.
"But moving here (from London to LA) and starting a life all over again was a lot harder than I had anticipated. I just didn't think it would be as isolating and daunting as it turned out to be.
"'I can honestly say that it took me five years to feel happy here."
That happiness came partly of the knowledge that, after years in her shadow, Rupert was now enjoying career success in his own right.
"In every picture that was taken of me at a party or a premiere, he'd be chopped off, and all you would ever see was his hand.
"At the world premiere in London, I had tears in my eyes, because we got out of our fancy car and all of the fans started screaming his name. The tables had really turned."