Among the invited guests will, of course, be Pippa's sister and brother in law, the Duchess and Duke of Cambridge, as well as other members of the royal family and friends, family and associates of hedge fund manager James.
However, they could find locals living in the area of the Berkshire church in which they are due to marry on May 20th seated along the pews.
The Church of England has recently published a guide on celebrity weddings and states that ordinary members of the public could have the right to attend the wedding mass.
The guide states that "a marriage is a public ceremony which at the least all parishioners are entitled to attend," but adds they are entitled to attend, "as long as there is available seating or standing room unless a genuine question of safety or security arises."
Stephen Borton, an ecclesiastical law expert and chief clerk of the faculty office of the Archbishop of Canterbury, told The Telegraph: "The document is pretty clear. Parishioners and those on the electoral roll have the absolute right to attend services of public worship, and they can't be denied access.
"Marriages are not a private event, they are public.
“It is a parish church and if any of the parishioners or any of those on the electoral roll wished to attend, they could not legally be refused. That of course does not extend to those from outside, such as the press."
It is believed that Prince Harry's girlfriend, Suits actress Meghan Merkle will not attend the church ceremony but will attend the reception. Pippa had reportedly issued a 'no ring, no bring' policy regarding guests.
James' brother Spencer Matthews, previously of Made in Chelsea fame, will also attend.