The countdown has begun to the celebrity wedding of the year this weekend as golfer Rory McIlroy prepares to get hitched to Erica Stoll in the luxurious surrounds of Ashford Castle in Co. Mayo.

A large number of catering staff entered the hotel on coaches today to begin preparations while there is a steady trickle of sightseers hoping to catch a glimpse of the famous guests. It is understood McIlroy is already at the castle and has been clay pigeon shooting with friends on the estate.

It's hardly a surprise that the glitzy wedding will be a star-studded affair with some very famous names rumoured to be on the guest list.

McIlroy is expected to marry Stoll at the Co. Mayo venue on Saturday

Along with fellow golfers such as Padraig Harrington and his wife Caroline, Niall Horan is almost certain to be attending. The former One Direction singer joined McIlroy on his stag weekend recently in Miami Beach in Florida.

The pair have been pals for some time now and Horan acted as caddy for McIlroy during the Par 3 Contest prior to the 2015 Masters Tournament in Augusta.

Niall Horan will be partying in Mayo this weekend at Rory McIlroy's wedding

Former Machester United player and Welsh international Ryan Giggs was spotted around Cong over the past few days, while there's also talk that Conor McGregor may attend the star-studded affair.

Meanwhile there's no shortage of other big name musical guests rumoured to be attending - as paid performers. 

Stevie Wonder is reportedly being flown to Ashford Castle to perform for the newly-weds. According to a report in the Daily Mail, ''Wonder will perform with an 18-piece band, at vast expense."

"They are flying in on Thursday and, separately, a piano and a piano tuner are arriving from London," a source is quoted in the newspaper.

No expense spared - Stevie Wonder is being flown in for the special occasion 

It's also rumoured that - despite playing in Manchester the same evening - Ed Sheeran will fly in for a surprise performance at the reception, while there has been talk that Coldplay could be making an appearance.

According to industry figures, Coldplay command around €700,000 for a private concert, while Sheeran's musical presence would set the couple back around €110,000.

Mind you that's all a drop in the ocean for the golfer. Last year Forbes put his net worth at $42.5 million.

Coldplay are heavily rumoured to be serenading the newlyweds

Further details are difficult to glean what with twenty-four security is in place around the five-star Mayo venue and staff said to have signed non-disclosure agreements to protect the privacy of the newly-weds.

Most of the guests are expected to arrive to the hotel by helicopter. The venue has long been a favourite of the couple who have spent the last two New Years at the luxury hotel.

Rory and Erica are no strangers to Ashford Castle

McIlroy met Stoll at the 2012 Ryder Cup in the United States when was working for the PGA of America and famously helped him reach the course on time to tee off after he overslept.

At the time, he was seeing tennis-pro Caroline Wozniacki.

McIlroy with her former fiancé Caroline Wozniacki.

The pair were later engaged however McIlroy called off the wedding in 2014 just days after the wedding invitations were sent out. 

Over a year-and-a-half later McIlroy popped the question to Stoll near the Eiffel Tower with an engagement ring rumoured to have cost around €500,000.