The pair couldn't have looked cuter while attending the premiere of a new nature documentary in London.
James -- the younger brother of Kate and Pippa Middleton -- joined Alizee at the London premiere of the celebrated new documentary The Elephant Queen on Thursday, and the happy couple posed for photos outside the event.
James, 32, looked positively regal in a plush dark blue velvet blazer over a white button-down shirt with a pair of dark denim jeans and brown leather boots.
Meanwhile, his 29-year-old ladylove beamed, wearing her long blonde locks down and rocking a burgundy corduroy jacket over a white top and beige skirt. She completed the ensemble with black buckled boots.
"She said OUI," he captioned a glowing image of himself and his new French fiancée standing in front of the idyllic, verdant landscape of England's Lake District.
He also addressed the fact that the news of his successful proposal had already broken the day before in English tabloids, joking, "Our secret is out but we couldn’t be happier to share the news."
James and Alizee, a financial analyst, first met at the South Kensington Club last year, when she said hello to Ella, one of James' many Cocker Spaniels.