The Anywhere singer, 33, gave her fellow punters an eyeful in the semi-transparent number which she wore beneath a long black coat.
Rihanna, 35, kept to the black theme as did actress Hannah Waddingham, 47.
Fellow star Anya Taylor-Joy, 27, went for red while Elizabeth Debicki, 33, was all white on the night.
All four headed for top fashion shows but Rita was hungry for cuisine.
We recently revealed Rita is set to release her most personal track yet – a country infused track all about her mum, Vera.
The Let You Love Me singer has teamed up with Aussie musician, and husband of Nicole Kidman, Keith Urban for Shape Of Me.
On the song, out January 29, Rita sings: “Yeah my mama got that heart, she said don’t let go of the parts that keep you younger.”
She later adds: “She said, don’t you worry, babe, you got my blood in your veins. I’ll be here to catch you when your world is just about to break.”
Rita’s mum works on the frontline in the NHS as a psychiatrist and mental health nurse.
The song originally appeared on Rita’s third album You and I but without Keith.