Kate first wore the shirt in 2019, during a trip to the Lake District.
She also wore it in the family’s Christmas photograph this year, taken at Anmer Hall.
The blouse has a ruffled collar, known as a “pie crust collar”, a style popular in the 80s.
It also has ladder-stitch detailing on the front of the shirt and on the cuffs.
Kate Middleton news: Duchess of Cambridge in Sezane – loved by French women
Kate Middleton news: Kate holds her own camera and wears an old favourite jumper
With the look, Kate wore a pair of Daniella Draper earrings. They were the £200 mini Cupid hoop earrings.
Sezane has been a runaway fashion success in the social media era.
The online-only fashion store takes French chic worldwide with reasonably priced sell-out collections.
Inspired by vintage garments, Sezane creates affordable versions, produced for a mass audience.
Operating out of Paris, the brand releases a seasonal collection four times a year.
Once a month there is a smaller collection and every Wednesday details of new collections and restocking.
Kate has a number of other items from the brand, including the Artemis belt.
The Duchess also owns Sezane’s Tulio jumper in merino wool.
Kate Middleton news:The Duchess owns Sezane’s Tulio jumper in merino wool
Kate Middleton’s fashion is one of the most copied in the world.
She is often on the top best-dressed lists around the world.
The Duchess of Cambridge is always championing new trends, albeit in a timeless style.
She seems to have adopted the idea of sustainability, a fashion buzzword linked to ethical production and environmentalism.
Personal stylist and fashion expert Samantha Harman spoke exclusively to Express.co.uk about Kate’s sustainable wardrobe, giving her analysis on how “thrifty” Kate is in reality, and what her fashion choices mean.
Samantha emphasises that “the royals are the best example of why what you wear matters”.
She said: “They use clothing to build and sustain relationships, convey messages and help causes they feel passionately about.
“When you’re on a world stage, how you dress is always going to be scrutinised,” Samantha added.
Source: EXPRESS CO UK