Olivia Henson has arrived at her society wedding of the year to the Duke of Westminster at Chester Cathedral.
Prince William, who is an usher at the ceremony, was cheered on by onlookers as he appeared at the Cathedral in Cheshire for the nuptials of his old friend Hugh Grosvenor.
The 7th Duke, 33, universally known as 'Hughie' to aristocratic friends, is estimated to be worth £10.42billion, making him the richest man under 40 in Britain.
He is the godfather to William's son Prince George and Prince Harry's son Archie. But while William is playing a major role at the service among 400 or so expected guests, Harry has remained in California.
Olivia, 31, looked stunning in her wedding dress and blue shoes as she arrived at the 11th Century Cathedral just before midday.
The bespoke embroidery design on her gown and veil was hand drawn by Emma Victoria Payne, featuring floral motifs and edgings from Olivia's great great grandmother's veil from around 1880.
The bride is wearing the Faberge Myrtle Leaf Tiara made for Grosvenor brides to wear on their wedding day. It has been in the Grosvenor family since its creation in 1906. Olivia's bouquet was made of flowers picked from the gardens of the duke's family home, Eaton Hall.
Princess Eugenie is among the many guests to have arrived at the event, while the Princess of Wales - who has been out the spotlight as she undergoes preventative chemotherapy - was not expected to attend.
Olivia Henson has arrived for her wedding to the Duke of Westminster at Chester Cathedral
Olivia Henson arrives for her wedding to Hugh Grosvenor, the Duke of Westminster at Chester Cathedral
Olivia Henson in her wedding dress outside the Cathedral for her wedding to Hugh Grosvenor
Olivia looked stunning as she arrived for her wedding to the Duke of Westminster today
Olivia walking through the stunning flower arch displayed on the entrance to the Cathedral
Olivia is getting wed to the Duke of Westminster at Chester Cathedral today
The bridesmaids arrive for the Wedding of The Duke of Westminster to Olivia Henson at Chester Cathedral
Olivia holds flowers as she enters Chester Cathedral for her wedding to the Duke of Westminster
The veil blew strongly in the wind, prompting gasps from the crowd, as she entered the cathedral
The bridge smiled in her wedding dress before walking into the Cathedral to marry the Duke of Westminster
The groom, Hugh Grosvenor (left), arriving at Chester Cathedral for his wedding to Olivia Henson
Prince William arriving at the Duke of Westminster's society wedding to Olivia
Princess Eugenie (pictured) arriving at the cathedral for the wedding of Hugh and Olivia
Princess Eugenie walking to the cathedral in Cheshire today before the ceremony
The bride stands in her wedding dress before entering the Cathedral in Cheshire
Olivia Henson arrives at her wedding to Hugh Grosvenor, 7th Duke of Westminster
Olivia looks elated as she arrives at her wedding to the Duke of Westminster in Cheshire
Olivia stops and smiles at the crowds before heading inside the Cathedral to marry the Duke of Westminster
The bespoke embroidery design on her gown and veil was hand drawn by Emma Victoria Payne
Olivia Henson arrives vin a vintage Bentley for her wedding to Hugh Grosvenor, Duke of Westminster
Olivia just before arriving at Chester Cathedral for her wedding to the Duke of Westminster
Olivia's bouquet was made of flowers picked from the gardens of the duke's family home, Eaton Hall
The bride wore blue shoes with her wedding dress to marry the Duke of Westminster
Olivia Henson arrives for her wedding to Hugh Grosvenor, the Duke of Westminster at Chester Cathedral
Olivia opted to make her shoes the 'something blue' at her wedding, which she paired with pink and purple flowers
The Duke 33, will wed Olivia Henson, 31, (pictured) in Cheshire today
Hugh smiles and waves as he arrives at the cathedral in Cheshire to wed Olivia
Charles van Straubenzee and his wife Daisy Jenks arrive at Chester Cathedral ahead of the wedding
Thomas Van Straubenzee and wife arrive for the ceremony today
The grooms mother, Natalia Grosvenor, Duchess of Westminster (left), arriving at the ceremony
Charlie Gilkes and his wife Anneke arriving at the cathedral for the society wedding of the year today
Guests arriving at Chester Cathedral in Cheshire for the wedding
Guests arrive for the wedding of Hugh Grosvenor to Olivia Henson at Chester Cathedral
More guests arriving at the society wedding of the year between Hugh and Olivia
A vehicle pulls up outside the cathedral ahead of the ceremony
Crowds gather outside Chester Cathedral for the Duke of Westminster and Olivia Henson's wedding today
Shortly before 11am, coachloads and minibuses of excited guests began arriving and filing into the side door of the Cathedral.
As they rounded the corner, many smiled and waved back to the crowds lining the streets, who were cheering their arrival.
William, dressed like others in morning suit, smiled as he exited a black minibus to head towards the building.
Guests joined the long queue snaking into the Cathedral, waiting to be shown to their seats by Prince William and the other ushers.
Harry, who would have been expected to attend today's service, has chosen instead to stay in California.
Miss Henson arrived at the Cathedral just before noon in a vintage 1930 8-litre Bentley owned by the Grosvenor estate.
After the ceremony finishes around 1pm guests will enjoy a lavish reception with a lemon wedding cake at the Grosvenor family seat, Eaton Hall, just outside Chester.
The Duke will pay for free ice cream, gelato and sorbet for Cheshire locals from three local independent cafes so they can join in the celebration.
Photos from this morning show excited royal fans forming a crowd outside the cathedral ahead of the Church of England ceremony starting at midday.
The fans have been gathering since 6am this morning, hours before the ceremony is due to start.
Maths tutor Catherina Rhodes, 59, of Chester, said: 'It's an exciting day. I have always loved the royal family especially the Queen.
'I was taken down to Buckingham Palace when I was aged six.
'My uncle worked at the stables and helped teach the Queen to ride. Since then I was entranced by the royal family.'
She added: 'It's great for the city.'
Pharmaceutical trainer Helen Jackson, 55, said: 'I went for a drink in the Grosvenor hotel last night and saw Princess Eugenie having a drink.
'So I know she's going to be here today.
'It's fabulous for [...] Chester.
'I came to see the royals when the Queen and Megan Markle came here just before.'
Pensioner Ann Beck arrived at 8am. She said: 'I wanted to come to support the family as they are from Chester and of course the royals.'
A staggering 100,000 flowers have been planted throughout the city - all paid for by the Duke - which will be donated to charity following the ceremony.
Prince William (right) and Hugh Grosvenor (left) attending the 2004 wedding of Edward van Cutsem and Lady Tamara Grosvenor at Chester Cathedral
Hugh is godfather to Prince Williams's son Prince George and Prince Harry's son Archie. Harry will not attend the wedding
A woman dresses up in wedding attire and a Union Jack scarf outside the cathedral
Crowds gather outside Chester Cathedral for the wedding today
A general view of police and well-wishers as they line the street near the cathedral
Police outside Chester Cathedral before the wedding this afternoon
Well-wishers line the street ahead of the wedding today
Police officers outside the cathedral in Cheshire today ahead of the ceremony
Crowds gather outside Chester Cathedral for the society wedding starting at midday
A general view of Chester Cathedral ahead of the wedding of The Duke of Westminster and Olivia Henson
Police vans in Chester Cathedral, where the wedding ceremony will take place
The Duke will pay for free ice cream for locals from three local businesses. Pictured left to right: Craig Fermor from Diddy Donuts, Valentina Aviotti from Krum Gelato and Stephen Young from Cheshire Farm Ice Cream
Scores of boxes of flowers were delivered to the cathedral by a fleet of vans
A large security cordon will be erected around the cathedral due to the presence of so many high profile guests. Pictured: Sniffer dogs in Chester
A workman carries a bundle of chairs through the garden at Chester Cathedral
Temporary scaffolding was also erected near the cathedral as workers trim plants
This week a floral arch was constructed around the huge West Door of the 1,000-year-old Cathedral in the heart of the city.
On a road into the city near the entrance to the Grosvenor Hospital, staff dressed a pair of mannequins in suit and wedding dress with photos of Hugh and Olivia's faces attached.
Given the presence of the heir to the throne at the event, security precautions have also been in evidence, with detectives seen chatting with local Cheshire Police officers outside the Cathedral this week.
Police sniffer dogs were seen checking drains around the precincts of the building for any traces of explosives.
Eaton Hall, a mock French chateau set in 10,872 acres of Cheshire (50 acres of which is elaborate formal gardens) is where the couple intend to live after they are married, and is the perfect place for a party.
Cheshire Farm Ice Cream, based in the heart of Chester Market, will be offering a range of Cheshire Farm single-scoop ice-creams or slices of a new lemon-sponge flavoured arctic roll.
The lemon-flavoured arctic roll has been specially created in acknowledgement of The Duke and Olivia's lemon-flavoured wedding cake that guests will be served at the wedding reception.
Ed Warrington, owner of Cheshire Farm Ice Cream outlets, said: 'As a local business we're delighted to be part of The Duke and Olivia's initiative to provide free ice cream to the public in celebration of their wedding.
'All at Cheshire Farm Ice Cream wish them the very best for their wedding day.'
The couple have been scrupulous about not giving away details of the reception and 'we have also been asked not to do any social media posting when we get there', said a guest.
It is likely to be a green event as both Hugh and Olivia are eco minded, and it is understood that flowers used at the ceremony and reception will be pressed and made into sustainable artworks afterwards, rather than simply being thrown away.
Olivia, who went to Marlborough College, like the Princess of Wales and Princess Eugenie, is senior account manager at Belazu, an environmentally friendly company which imports chef-quality, sustainably-sourced ingredients.
Hugh has increasingly started to initiate various eco-friendly practices, including renewable energy projects, green building codes and biodiversity conservation efforts.