During the 2019 Australian U/21 championships held at the Brunswick Club I had occasion to referee a frame where, by the process of the colours being potted and their spots being occupied at the time, the green ball had ended up on the Centre Spot. The Pink was on The Spot and a number of red balls were clustered around the Pyramid Spot. The Black, Blue, Yellow and Brown balls were on or near the baulk spots so that those were also unavailable.
The very talented Tasmanian junior, Alex Pace was at the table and on a small but substantial break as the colour of choice after each red had to be, or had contrived to be the green. The stage had been reached where there were now only two red balls near the Pyramid Spot with one almost directly on it and the other in close proximity. The third last remaining red had been potted, the green again taken as the colour of choice and returned to the Centre Spot as the only spot available. Alex then took the red which was directly on, or very close to the Pyramid Spot, was successful with the stroke and played exceptionally well to manoeuvre the cue ball with screw to just the baulk side of the Centre Spot and between that spot and the side cushion for perfect position to again pot the green and gain what he thought would be a good position to pot the final red.
This was also achieved but now the green had to be replaced on the table, as it had every other time, on either its own spot or the highest available. Because the red covering the Pyramid Spot had been removed this now became the highest, usurping the Centre Spot. As I spotted the ball Alex reared back in amazement and shock, then the realisation came to him that the correct decision as to the placement of the ball had been made and that he was now snookered on the last remaining red.
As the green had been spotted 4 or 5 times on the Centre Spot a certain complacency of where it should or would be placed, or a lack of concentration of how the game is administered, or too much concentration on the break to the exclusion of other important things, had brought him undone and is a lesson, not only to players caught in similar situations, which is not that uncommon, but also to referees, to be vigilant at all times and to administer the rules as demanded and avoid as many mistakes as possible. A lapse of concentration in that circumstance by a referee and a replacement of a ball in the wrong place would have created a very unfair advantage for the striker and a very unfair disadvantage for the non-striker.