With an odd number – 73 players made the cut – remaining in the field Waring was given a marker to play alongside as he teed off at 9.35am and that prize was handed to O'Neill, who missed out in qualifying for the tournament outright last month.
The Royal Portrush club shop closed so staff could watch McNeill tee off with a somewhat understandably nervous low, left shot off the first.
Despite a healthy breeze helping over the opening few holes birdies were hard to come by with just two managed by the first five groups.
One of those went to the only remaining Northern Irishman left in the field Graeme McDowell, playing in the most high-profile group of the morning alongside two-time Masters champion Bubba Watson, as he took advantage of the par-five second to move to level par.
With winds expected to strengthen later in the day it was likely to mean an even more testing afternoon for the leaders.
Ireland's Shane Lowry and American JB Holmes were last off at 3.50pm, with the pairing of Tommy Fleetwood and Lee Westwood just ahead of them as they looked to strengthen their chances of becoming the first Englishman to win the Open since Nick Faldo in 1992.