The 65-year-old royal married the Prince in 1986. They became parents to two daughters - Princess Beatrice and Princess Eugenie - before splitting in 1992 and divorcing in 1996 - but they have remained close friends over the years and still live together at the Royal Lodge in Windsor.
Sarah is adamant she has no regrets about the relationship.
She told The Sunday Times newspaper: "I was totally and utterly in love with Andrew. I would do it all over again, 100 per cent.
"He's the best, a great man with a great heart, and kind."
Sarah has stood by Andrew throughout his troubles over the last few years as he faced the fallout over his friendship with late paedophile billionaire Jeffrey Epstein and claims he had sex with one of the financier's trafficking victims Virginia Giuffre – which he denied - and she's adamant she will always be there for him.
She said: "Our wedding was the best day of my life. But I gave up my anonymity that day. I was able to because love conquers all. It's still with us today.
"I won't let him down. He supports me as much as I support him. He's supported me through thick and thin, not just marriage or divorce."
Sarah previously revealed she made a promise to the late Queen Elizabeth that she would always take care of Andrew.
During an appearance on TV show Loose Women, she explained: "We are longer divorced than married and I believe in the three C's – communicate, compromise and compassion.
"That's what I do with (Andrew.) We get on because, in the darkest time of my life, he was always there for me.
"In the darkest time of his life, I will be there for him. The Queen of England was there for him - his mum.
"I said to his mum before she died, 'I will be there for him, I will help him on his journey.' We've all got journeys; we just need to be there with kindness and no judgement."
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