A total of 14 helicopters were spotted landing at the venue in Cong, Co Mayo since yesterday as guests including One Direction star Niall Horan and golf stars Shane Lowry and Sergio Garcia arrived for the lavish wedding.
Horan and Garcia reportedly arrived at Knock airport on Friday while JP McManus arrived by helicopter and Paul McGinley arrived at lunchtime today.
Stevie Wonder called into a CompuB store in Galway yesterday, further fuelling rumours he'll perform at the nuptials (although some local fishermen are convinced they heard him playing Friday night) while Chris Martin, Jamie Dornan and Ed Sheeran are rumoured to also attend.
Details are scant for assembled press as security is very tight around the grounds.
Staff had to sign non disclosure agreements and have their mobile phones removed before working at the 13th Century castle, and there are reportedly three layers of security at four different access points at the venue and perimeter patrols taking place.
Golf star Rory (27) and Erica (29) have been residing at the castle since Wednesday with Rory taking part in clay pigeon shooting and both he and his fiancee yesterday enjoyed a falconry display in the grounds of the 360 acre 13th century estate.
According to the Irish Daily Star the couple reportedly turned down two magazine deals offering €1m for exclusive photos of their big day.
A fireworks display is believed to be planned for this evening after guests enjoy a gourmet menu from executive chef Philippe Farineau.