"HAVING A FIELD DAY " : THE TRUE ORIGIN OF THIS SAYING........... ( Research by Pun )

Most people use this figurative expression for a day or occasion or time of particular success , often associated with great excitement in the world of competitive sports. However , the myth that such a saying was first used by the military , to describe a day when troops were engaged in manoeuvres , exercises or reviews out in the field , needs to be dispelled immediately.Often the area or place in which military operations were carried out were nothing like open fields. The army in particular would use barren or rocky terrains , woods,  along with derelict sites where houses had been reduced to rubble. 
My research has shown that the expression was first coined at the Long Buckby Bridge Club during a pairs tournament in 1902. The winning pair , a couple of well-to-do farmers , scored 76% , having crucified the opposition from start to finish. As one laid his blood stained hands on the trophy, he was heard to remark to his partner " In all my life  I've never come across so many useless tossers all gathered together in the same place ....... in fact any half-decent player would have a field day against this load of bunnies ". 
Consequently from that day on big hitters would turn up at tournaments referring to all other competitors as rabbits , expecting of course to have a field day of remorseless, enjoyable , highly rewarding slaughter .