Police papers, caught by an eagle-eyed photographer, have offered a glimpse into the intense final preparations for what's being dubbed the wedding of the year.
A police officer has been pictured holding a folder of documents, with the front page revealing the finer details of the event's planning diary - including the tuning of the organ, security searches and the start of a wedding rehearsal.
The police documents offered a glimpse at the increasingly strict security measures surrounding the wedding of the year, as fencing, CCTV and sniffer dogs were installed on site for the rehearsal today, the Daily Mail reports.
The officer was pictured on the Englefield estate with the documents - inadvertently exposing a breakdown of timings for the final run-through ahead of Pippa Middleton's wedding to hedge fund manager James Matthews in Berkshire on Saturday.
It shows a step needed to be added to the church lectern, while 'protected principals' - thought to refer to wedding guests - were flanked by security personnel ahead of the rehearsal.
The guest list will include the second and third-in-line to the British throne along with a host of VIPs and celebrities, so the Middleton and Matthews families are taking no chances when it comes to safety and security.
The scale of the event has become ever more apparent as Pippa's big moment draws near, with enormous cherry blossom trees visible on Friday inside the 140ft glass marquee on the Middletons' Berkshire estate that will house the reception.
Stage-style lighting was also visible rigged to the ceiling of the structure.
But The Duchess of Cambridge's younger sister, who will tie the knot with her financier boyfriend on Saturday morning, has also gone to great lengths to ensure security is tight on the estate surrounding St. Mark's church.
A team of police, security officials and even dogs were spotted on the Englefield estate on Friday afternoon ahead of tomorrow's ceremony.
Two men dressed in black were seen installing surveillance cameras on trees lining the footpath which surrounds the picturesque Bucklebury wedding venue.
A large police car was also spotted near St Mark's Church, with metal fencing securing the guests' route into the church.
While Saturday's ceremony will take place on the Berkshire estate, the bride's parents are hosting the reception and have forked out for a 140ft-long glass marquee in their garden.
Pippa's parents, Carole and Michael Middleton are believed to be picking up the bill for the lavish nuptials which are estimated to have cost anywhere between £200,000 and £500,000 (NZ$376,000 and NZ$941,000).
It's no surprise the couple, who got engaged last summer, want to ramp up security efforts; guests include the Duke and Duchess of Cambridge as well as Prince Harry.
Harry's girlfriend, Suits actress Meghan Markle, is also believed to be making an appearance after flying into London from her home in Toronto this week.
Kensington Palace have also confirmed that Prince George will be a page boy and Princess Charlotte will be a bridesmaid.
A Green Parlour florist van - the same company that Kate enlisted for the Royal Wedding in 2011 - was seen arriving at St Mark's Church on Friday ahead of Pippa and James Matthews's wedding.
The last-minute preparations come after workmen appeared to be making some last-minute improvements to the church and gardens where Pippa and James will tie the knot.
The installation of the barriers comes after a fleet of Bentley Bentayga 4x4 were delivered to Englefield House earlier this week, which could well be the cars that will ferry guests from the church to the Middleton family home a few miles away for the evening reception.
A gardener was seen mowing the lawns for the second time this week, whilst workers were spotted cleaning and fixing the church's sign - preparations that are thought to be taking place ahead of the society wedding of the year.