"I'm engaged," Monk shared on Instagram at the time.
"I honestly can’t thank you enough for all the love and support. I know I have the coolest people following me and you’ve always had my back and I feel so cared about. You’re absolute bloody legends," she continued.
"I’m not very good at being mushy. I’m trying to say I absolutely adore you. Joshua and I are so happy."
Gross, 37, who is a neurosurgical robotics consultant, also shared the news on his own Instagram page, writing: "Luckiest guy in the world."
Now, almost one month after announcing their engagement, Monk has shared how Gross proposed on Christmas Day at home while enjoying a cup of coffee, in an interview for Stellar magazine.
"He knelt down, and I just said yes before he even asked," she told the publication.
"He's like, 'Hang on, I've got stuff to say!' And I'm just like, 'It's good, yes!' And then I cried."
Gross also revealed that he was "a little heartbroken" when he saw paparazzi photos of him leaving a jeweller in November, which spoiled the surprise.
"I'd gone through six months of cloak-and-dagger secrecy to get this done without Sophie knowing because I wanted her to have a good surprise," he explained.