Thousands of well-wishers gathered in Chester for the wedding of the Duke of Westminster, where the Prince of Wales acted as an usher.
Hugh Grosvenor, the godson of King Charles III, married Olivia Henson at the city's cathedral earlier.
The 33-year-old duke is godfather to Prince George, but the 10-year-old could not join his father at the ceremony due to it falling on a school day.
Two women were removed from the crowd by police after an orange plume was deployed from a fire extinguisher-type device as the couple left the cathedral.
Campaign group Just Stop Oil said two of its supporters had used the device to project powder paint near the cathedral entrance as the newlyweds made their way to a car.
Cheshire Police said two women, a 69-year-old from Manchester and 73-year-old from Suffolk, had been arrested on suspicion of public order offences and remained in custody.
The duke is regarded as one of the richest people in the UK, with a fortune of about £10bn, while his bride has worked in the sustainable food and drinks industry.
Along with being a godparent for Prince George, he is also reported to be godfather to the Duke of Sussex's son, Prince Archie.
Prince Harry, who was an usher with his brother at the wedding of the duke’s sister Lady Tamara Grosvenor in 2004, is understood not to have attended the service by mutual agreement.
The King and Queen Camilla did not attend the service, after travelling to Normandy for the D-Day commemorations on Thursday.
The Princess of Wales, who is receiving treatment for cancer, also did not attend.
The bride wore a dress and veil designed by Emma Victoria Payne, embroidered with floral motifs and edgings from Ms Henson's great-great-grandmother's veil from about 1880.
The 31-year-old also wore a vintage tiara, incorporating a myrtle leaf design, which was made by the prestigious Russian jewellery craftmakers Fabergé for Grosvenor brides and has been worn on their wedding days since 1906.
Her bouquet was made of flowers picked from the gardens of Eaton Hall, the duke's country house.
Members of the public began arriving outside the cathedral from early in the morning, bringing camping chairs and picnics.
By the time of the service, thousands were gathered outside the cathedral and in the surrounding streets and many of them witnessed the protest as the couple re-emerged.
Barbara Williams, 81, from Cheshire, who was standing next to the protesters in the crowd, said she felt "a bit shaken after it".
She said she and her friend Andrea Machin, 56, had been "standing next to them all day".
"They were already here when we arrived at 07:00 [and] they had shopping trolleys with them," Ms Machin said.
"Everyone was watching the bride and groom and then we just saw orange and they had what looked like a fire extinguisher with them.
"The police realised quite quickly what was happening and pulled them out.
"It happened just as William was coming out of the door."
In a statement issued by Just Stop Oil, the protesters said weddings were "a time of coming together in celebration to make a commitment to the future", but for "countless millions around the world there is no future unless we come together to stop oil and gas".
A representative for the duke and Ms Henson said it meant "a lot" for them to marry in Chester, due to the Grosvenor family's "long and close personal connection to both the cathedral and the city".
They said the couple had "made a conscious effort to involve local and regional suppliers in several aspects of the day".
"The couple have also been moved by the messages of support they have received from around the region and are hugely grateful that people want to share in their happiness," they added.
The city’s annual Summer Flowers project has been funded by the couple, with 100,000 flowers planted as part of the wedding celebrations and they have also paid for free ice cream and sorbet from three local independent businesses to be given to visitors to Chester city centre through the day.
Poppy, a student at the University of Chester, was one of those indulging in a free ice cream.
She said it was "great to see the people and the businesses together".
"It’s really fun to get the students out in the city and involved," she added.
The duke inherited his title and control of the Grosvenor Estate at the age of 25, following his father's death in 2016, and the couple announced their engagement in April 2023 after being together for two years.
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