"Love to everyone who made this night so special x," Tweeted Professor Green, proving the night had been a success, before the couples' guests began tweeting their messages of thanks on the social networking site.
Bride-to-be Millie, 23, was as elegant as ever in a white snakeskin dress that featured sheer panels at the collar and hem and accessorised with bright red lipstick and scarlet stilettos. Professor Green, 29, kept his look more casual, choosing jeans and a printed white jumper for the occasion.
Millie's Made in Chelsea co-stars, including fashion blogger Rosie Fortescue and PA Alexandra 'Binky' Felstead, helped the star celebrate her engagement.
T-shirt designer Oliver Proudlock was also seen leaving the Soho venue with fellow Made in Chelsea star Louise Thompson.
Singer Emeli Sande, who collaborated with Professor Green on their track Read All About It, also joined the party as did musician Elle Eyre. Rapper Example, whose real name is Elliot John Greave, brought his Australian fiancée Erin McNaught to the bash.
Millie and Professor Green confirmed the news of their engagement via Twitter when the makeup artist and reality TV star posted a photo showing off her beautiful double-banded engagement ring.
"If I could scream loud enough for the whole world to hear I would," she wrote next to the picture.