The very 70s inspired dress had voluminous sleeves and long cuffs. Nipped in at the waist, her tiny midriff was accented by large ruffles on the shoulders.
Kate appeared to be wearing her navy suede Prada heels.
She held a new bag, thought to be the Ludlow Concertina Crossbody Bag from Smythson, £625.
Her jewellery for the event was a number of pieces she already owns and has worn on a number of outings.
Around her wrist snaked her Halcyon Days Maya Torque bracelet and from her ears hung the Simon Rocha Faux Pearl Curb-Chain Earrings
Kate Middleton news: Duchess of Cambridge wows in 70s dress just like Diana
Kate’s hair was styled in voluminous waves.
The Duchess’s dress was by Alessandra Rich, a brand she has worn before. It is the petal print dress, and dresses from this brand cost in the region of £1,500.
The designer is hugely inspired by the late 70s and 80s, which is why Kate’s look tonight will remind many of those worn by Princess Diana.
Diana frequently wore dresses with ruffles and print, as was fashionable at the time.
Similar dresses worn by Diana include a blue velvet dress with a white lace trim around the neck.
She wore the gown in 1981, also to a premiere.
Kate, William and their three children George, Charlotte and Louis were all out for a festive trip to the pantomime.
They watched the performance at The London Palladium in the West End.
Kate Middleton news: The very 70s inspired dress had voluminous sleeves and long cuffs
The show, Pantoland, stars Julian Clary and Elaine Page.
Kate wasn’t the only one dressed smartly, Louis, two, wore a blue cardigan.
George, seven, wore a jumper while Charlotte, five, wore a grey and black tartan dress.
Source: EXPRESS CO UK