Princess Eugenie has portrayed the proposition from her long haul beau Jack Brooksbank as an "immaculate minute".
The Queen's granddaughter said it was a "total shock" when Mr Brooksbank got down on one knee before a well of lava as the sun was setting in Nicaragua not long ago.
The princess revealed to BBC's The One Show that she cried and was "over the moon".
The wedding will happen at St George's Chapel, Windsor Castle, in the harvest time.
It will be the second imperial wedding at the house of prayer this year - Prince Harry and Meghan Markle are expected to wed there in May.
Princess Eugenie said the couple were investigating a lake while the sun was setting before the proposition.
She stated: "The lake was so excellent. The light was only an uncommon light I had never observed. I really said this is an unfathomable minute, and afterward he popped the inquiry, which was extremely astonishing despite the fact that we have been as one seven years.
"I was over the moon.
"[It was a] finished astonishment. Be that as it may, it was the ideal minute, we couldn't be more joyful."
Mr Brooksbank stated: "It was astonishing."
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The princess met the previous supervisor of Mayfair club Mahiki on a skiing trip.
"We met when I was 20 and Jack was 24 and began to look all starry eyed at," she said. "We have similar interests and drive forever."
Mr Brooksbank said it was "unexplainable adoration".
"I adore Eugenie so much and we are simply so glad and over the moon for what is to come," he said.
The princess included: "Granny really knew comfortable starting [of the engagement]. She was extremely glad similar to my granddad."
Engagement photos of the couple, taken in the Picture Gallery at Buckingham Palace, were discharged after the declaration.
In the photos, Princess Eugenie is wearing a dress by Erdem, shoes by Jimmy Choo and a ring containing a padparadscha sapphire encompassed by jewels.
Mr Brooksbank stated: "I found a ring in a gem specialists and after that proposed to Eugenie without it and returned and we outlined the precious stones around this padparadscha sapphire.
"Also, what's astounding about it is that it changes shading from each unique edge that you take a gander at it, which is the thing that I consider Eugenie.
"That she changes shading and is simply so astounding."
The padparadscha is an uncommon pink-orange sapphire and is typically found in Sri Lanka.
The Natural Sapphire organization said the pearl was named after the shade of a lotus bloom.
Princess Eugenie's ring is comparable fit as a fiddle and configuration to her mom's wedding band, which had a red ruby as the focal stone.
Twenty-seven-year-old Eugenie is the second little girl of Prince Andrew and Sarah, Duchess of York, and is eighth in line to the honored position.
She will keep her imperial title when she weds Mr Brooksbank and will have the choice to take his surname.
The princess works in expressions of the human experience as an executive at exhibition Hauser and Wirth.
In a progression of tweets, Sarah Ferguson complimented her little girl and her life partner, calling the declaration "Add up to satisfaction!".!