Kate, 37, and the Queen, 92, shared a blanket in the back of the car as they pulled up at King’s College London, where they will reopen Grade II-listed Bush House.
The Duchess was elegant in a grey Catherine Walker coat, believed to be a new bespoke addition to her wardrobe, which she teamed with her new favourite £510 Gianvito Rossi block heels and a black Mulberry clutch.
In a rare move for such an outing, Kate, 37, completed her outfit with a hat, which is likely to be a sign of respect to the monarch.
Meanwhile the Queen, 92, plumped for a rose pink coat by Stewart Parvin and matching Rachel Trevor-Morgan hat with beautiful floral detailing at the brim.
While the Queen and the Duchess of Cambridge have attended dozens of events together, it is their first without any other member of the royal family.
In 2012 the pair visited Leicester as part of the Diamond Jubilee tour but were joined by the Duke of Edinburgh. However they did make individual stops on the schedule without him, including watching a student fashion show.
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The Queen and the Duchess of Cambridge shared a blanket as they arrived at King’s College London in the back of a car
The Queen and the Duchess of Cambridge have arrived at King’s College London for a joint engagement
Keep it chic like the Duchess of Cambridge in Catherine Walker
Catherine Walker grey dress coat
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Catherine Walker is a go-to for the Duchess of Cambridge on big occasions, so it was no surprise she turned to the London-based label to dress her for a rare joint engagement with the Queen in London today.
The fit and flare shape of this grey coat dress is classic Kate, and we love the contrast collar. The buckled belt shows off her figure perfectly, and when teamed with black tights, her new favourite Gianvito Rossi block heels, a black Mulberry clutch bag and a matching headpiece, it’s a very sophisticated look.
It’s a new addition to Kate’s wardrobe, and it looks like it was made just for her, but click (right) to find out more about Catherine Walker’s designs.
Or go grey in one of the dresses we’ve rounded up to help you recreate this look. How sweet is the contrast collar on this M&S option?
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The Duchess of Cambridge looked elegant in a Catherine Walker coat, black hat and black heels for the outing
Following protocol, the Duchess of Cambridge walked behind the Queen as they made their way into Bush House
The Queen and the Duchess of Cambridge appeared in excellent spirits and smiled as they arrived at Bush House
The Queen brought a splash of colour to proceedings in her pink coat and waved to royal well-wishers as she arrived
The Queen smiled as she stepped out of the car, dressed in a coat by Stewart Parvin and matching Rachel Trevor-Morgan hat
The Queen and the Duchess of Cambridge were given a warm welcome as they arrived at King’s College London today
The Duchess of Cambridge and the Queen will be given a tour of some of the facilities of Bush House during the engagement
The Duchess of Cambridge smiled as she stepped out of the car, while the Queen turned her attention to the well-wishers
A crowd gathered to watch the royals drive through the gates into the campus of Bush House, pictured
The outing took place in March, shortly before William and Kate’s first wedding anniversary.
Later that year the Duchess of Cambridge joined the Queen at Fortnum & Mason for an event launching a military initiative, where they were joined by the Duchess of Cornwall.
Today the Queen and the Duchess of Cambridge appeared in excellent spirits as they arrived at Bush House, which previously served as the headquarters for BBC World Service but is being leased by King’s College London.
It marks the newest building as part of the university’s Strand Campus.
Kate and the Queen could be seen sitting with a blue blanket over their laps as they arrived in the back of a car.
There was much fanfare, with well-wishers crowding outside the gates to the building and some even standing on bollards in the hope of getting a better glimpse of the royals.
Following royal protocol, Kate waited for the Queen to leave the car before exiting the vehicle herself. She continued to walk behind the monarch as they made their way into the building.
The Duchess of Cambridge followed royal protocol by waiting for the Queen to leave the car before exiting herself
The Duchess of Cambridge stepped out in one of her favourite shapes of coat as she joined the Queen in London today
The Duchess of Cambridge wore her new favourite Gianvito Rossi block heels and carried a Mulberry clutch
The Queen’s Rachel Trevor-Morgan features beautiful floral detailing, left and right, which was on display as she arrived
The Queen and the Duchess of Cambridge were greeted outside Bush House, the latest edition to the Strand Campus
The Duchess of Cambridge brought a more formal take to her outfit with a hat, which she wouldn’t typically wear on such an outing
The Duchess of Cambridge wore her long brunette locks in soft waves for the outing with the Queen in London today
The Queen, who is patron of King’s College and visited in 2002 and 2012, will tour the facilities with Kate and meet supporters of the development.
They will view a robotics demonstration, including robotic surgery, and a demo showing how sensors made from textiles can measure useful information about the body.
They will also visit a virtual trading floor and meet students from the Entrepreneurship Institute, which supports entrepreneurial thinking, skills and experiences amongst King’s students, staff and alumni.
The Queen and the Duchess of Cambridge arrived at Bushy House, King’s College London, on Tuesday morning
The Queen climbed out of the car ahead of the Duchess of Cambridge, who followed respectfully behind
The royals were greeted by a crowd of well-wishers who had waited outside the building, hoping to catch a glimpse
The Duchess of Cambridge has rarely attended an engagement with the Queen without her husband the Duke of Cambridge
The Queen, patron of King’s College London, and the Duchess of Cambridge were greeted as they arrived at Bush House
The Queen is expected to unveil a plaque to formally open Bush House.
Later, Kate will visit the Foundling Museum to understand how it uses art to make a positive contribution to society by engaging with vulnerable and marginalised young people.
The museum tells the history of the Foundling Hospital, the UK’s first children’s charity and public art gallery.
Kate, who visited the museum in 2017, is expected to view Bedrooms of London, a photography exhibition that documents the living conditions of London’s most disadvantaged children.
The Duchess of Cambridge joined the Queen and the Duke of Edinburgh on an outing to Leicester in March 2012, pictured