Mel C chose the full-length black Perrault gown from Posh's Autumn/Winter 2009 collection. And completed the elegant look with a stylish plait.
Thirty-six-year old Mel was nominated in the musical category for her part as Mrs Johnstone in Blood Brothers, of which she is a month shy of completing a six-month run.
While the mum-of-one missed out on picking up a trophy, successful on the night was Rachel Weisz. The Hollywood star was awarded the best actress gong for her role as of Blanche DuBois in A Streetcar Named Desire.
Other nominees putting in glam appearances at the Grosvenor House bash included Keira Knightley, who opted for a full-length screen-print frock, and Kim Catrall.
The Sex and the City star, who has been appearing in Noel Coward play Private Lives, went back to the Eighties with a white creation featuring an oversize asymetric neckline detail.