The Queen and Meghan, the Duchess of Sussex, are opening the Mersey Gateway Bridge as they attend their first joint engagement.
Meghan, 36, is passing another royal milestone, days after her first balcony appearance on Buckingham Palace on Saturday, during Trooping the Colour.
She and the Queen cut the ribbon to open the bridge over the Mersey and unveiled a plaque to commemorate the event.
The opening took place at the Catalyst Museum, which offers a bird's eye view of the new crossing from the glass top observation gallery.
This is her first event without her husband, Prince Harry, by her side.
Her first solo visit with the Queen also comes much sooner after her marriage into the family than her sister-in-law's. Kate, the Duchess of Cambridge, first accompanied the Queen on a visit to Leicester in 2012, during her Diamond Jubilee tour.
It took place in March, around 11 months after Kate and William married in April 2011.
Ahead of their engagement today, the Queen and Meghan arrived by Royal train before travelling by car to the bridge, a £1.86bn project, which should ease traffic between Runcorn and Widnes.
They were greeted by local dignitaries as the street around Runcorn station was lined by schoolchildren and well-wishers who waved flags and applauded as they arrived.
Also on hand to welcome them was Grange Hill, Hollyoaks, and Brookside creator Phil Redmond, whose wife Alexis is the High Sheriff of Cheshire.
He joked he should have asked Meghan if she'd like a role in Hollyoaks, adding: "I didn't ask her, but there's still lunch yet. She'll have to go through the audition process like everybody else."
His wife said: "It's fantastic to have them here and it's a big day for Cheshire."
Mick Noone, former operation director for the council, said the Queen asked how long the six-lane bridge had taken to build, while Meghan described it as "magnificent".
Queen Elizabeth wore a striking green outfit and hat for the event, as the country remembers the victims and survivors of the Grenfell tower fire by going green for Grenfell.
Her outfit is by Stewart Parvin and hat is by Rachel Trevor Morgan. She is carrying her trademark black Launer handbag and opted for trusty black patent Anello & Davide low heels.
Meghan was wearing Givenchy, the designer label behind her wedding gown.
She wore a cream dress with a cape, adding a thin black belt around her waist. She carried a clutch bag, and opted to leave her hair down instead of wearing a hat. She also towered over the Queen in Sarah Flint stilettos.
Although the Queen wore gloves, appearing to be neutral to match her granddaughter-in-law's dress, Meghan did not.
The royal pair took part in a minute's silence to remember the Grenfell victims at 12 noon, the moment adding a sombre tone to an otherwise lighthearted day.
After the unveiling and ribbon cutting, Meghan and the Queen watched a performance by local schoolchildren called Bringing Communities Together, by performers from the Andrew Curphey Theatre Company.
They appeared to be sharing a joke as they sat next to each other, and Mr Curphey said Meghan was "really calm considering it was her first official engagement with the boss".
He added: "The children have been hugely excited and it's been a massive treat for them.
"The Queen said she thoroughly enjoyed it and it was lovely to see the history of the bridge on the videos.
"As Meghan walked away from me she turned back and said 'the children did great by the way'."
The Queen and the Duchess were presented with flowers by Savannah Cafferty, 11, and Alarni Wain, who is celebrating her eighth birthday. She said both royals wish her a happy birthday.
The royal pair then went on to Chester, 20 miles away, for further engagements.
They attended the official opening of Storyhouse, a library, cinema and theatre complex, where they had a tour of the building.
They will meet a Syrian settlement group engaged in craft work, and watch a performance by Fallen Angels, a dance theatre company for people who are recovering from addiction.
In the theatre, they will see a medley of songs from Storyhouse's latest production, A Little Night Music.
The Queen and Meghan will have lunch at Chester Town Hall, as guests of the City Council, concluding their visit.
Meghan married Prince Harry in Windsor in May and since then, has joined the royal family for Trooping the Colour, also known as the Queen's birthday parade, and has announced her first royal tour.
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