Almost all Britain's senior royals are expected to attend although Prince Charles's wife Camilla will be absent as she has a prior engagement in Scotland.
The prince is set to attend the ceremony, but will then head off to a Military Rehabilitation Headley Court Gala Dinner in London later in the day.
Once married, Princess Eugenie and Mr Brooksbank will be taken on a short carriage procession along part of Windsor High Street.
"Although Princess Eugenie's engagement ring is reminiscent of Catherine's with the large centre sapphire and diamond surround, it's a classic design for a royal engagement ring and not likely an intentional similarity", royal commentator Eloise Parker said.
The traditional "to obey" has been taken out.
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"Most Brits opposed taxpayer funding of Prince Harry's wedding but as with all royal events were forced to accept it", a spokesman for the group said.
While the rest of the Royal Family will be enjoying the festivities at Windsor Castle, Camilla is understood to have not wanted to let the children down.
As per tradition, Queen Elizabeth II will be the last royal to arrive. This week, the members of the bridal party were revealed, confirming Princess Beatrice's role as Maid of Honour for her close friend and confidante.
According to BBC News, 1,200 members of the public have been invited to the wedding at Windsor Castle.
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