The Duchess of Cambridge's sister Pippa Middleton will marry her millionaire groom James Matthews today at an event dubbed the society wedding of the year.
The couple will say their vows in a picturesque Berkshire church before a congregation which will include the Duke and Duchess of Cambridge, their children Prince George and Princess Charlotte, Prince Harry and other close family and friends.
The event is likely to see hundreds of royal fans, press and public descend on the quiet village of Englefield, near Reading, which is home to St Mark's Church, where the ceremony will take place.
Details of the wedding service, reception and celebrations have been kept under wraps by organisers but there has been speculation in the press the day will cost Pippa's parents Carole and Michael Middleton hundreds of thousands of pounds.
An expensive glass marquee is believed to have been hired for the event, as have vintage cars and modern prestige vehicles - and posh portable toilets.
Reports suggest it will be a lavish affair, with a nod to the groom's Scottish connections included in his outfit, entertainment and the food, with haggis on the menu along with Scottish lamb and whisky, while there will also be a piper and a Spitfire flypast.
The young royals George and Charlotte will play starring roles as a page boy and bridesmaid, while royal watchers will be waiting to see if Harry brings his American actress girlfriend Meghan Markle.
Kate's controversial uncle, Gary Goldsmith, who was a guest at the Duke and Duchess of Cambridge's 2011 wedding, is also said to be attending.
James's brother Spencer Matthews, a reality TV star who was a regular in the show Made In Chelsea, is likely to be best man.
But Matthews's girlfriend, reality TV star Vogue Williams, will not be attending due to a "prior engagement", her spokesman said, adding she "wishes Pippa and James all the best on their special day".
Security is expected to be tight with several senior royals attending, guarded as usual by Scotland Yard royalty protection officers.
A Metropolitan Police spokesman said: "We are not prepared to discuss matters of security."
No-fly zones, banning aircraft including drones, balloons, kites and parachutes, have been imposed over Bucklebury and Englefield between 6am on Friday and 3pm on Sunday.
The details of Miss Middleton's wedding gown have also been a tightly held secret, with the names of a number of designers being put forward by royal watchers, from Amanda Wakeley and Jenny Packham to Oscar De La Renta, Giles Deacon and Alexander McQueen.
The Rev Nick Wynne-Jones, who is the church's resident priest, is expected to officiate at the wedding.
With the Middleton family home just a few miles away in the village of Bucklebury, the couple and their guests will not have far to travel for the reception, which is reportedly being staged in the grounds of the property.