Ever-stylish Kate certainly didn't disappoint her fashion fans — she wore a showstopping Roland Mouret cream gown with a glittering statement necklace.
It isn't the first time she's worn the form-fitting cream coloured dress, which features a daring thigh-high split.
The famously-thrifty Duchess debuted the classic Lombard number from the designer's RM collection at a black tie event in May 2012.
On Thursday night she teamed the stunning design with an understated black clutch bag and matching heels.
The fashionista royal wore her glossy, newly-darkened locks in a simple, chic ponytail.
The royal couple were greeted by rapturous applause from fans who had gathered at the venue to catch a glimpse of them on the red carpet.
The pair left their five-month-old baby boy Prince George tucked up in their Kensington Palace home to attend the glamorous event.
Before the performance the charming couple met Idris Elba, who stars as Nelson Mandela, and Naomi Harris who plays his wife Winnie Mandela.
The Duke and Duchess also met Mandela's daughter Zindzi Mandela as well as a selection of trustees of the Cinema and Television Benevolent Fund.
Zindzi's sister Makaziwe said on Wednesday that her anti-apartheid legend father, who was hospitalised for a lung infection in June, was "strong" despite being "on his deathbed".
The royal premiere is the fund's principal fundraising event and sees money raised from the event going directly to the charity which supports the industry's employees and their families in times of hardship.
The film, which was made with the full support of the former South African leader, tells his extraordinary life story from his childhood in a rural village through to his inauguration as the first democratically elected president of the African nation.