Slieve Gullian/Camlough?
Easy to confuse them!
I was once tasked with a patrol drop to a grid. The patrol comprised the CO, Ops Offr, 2ic and QM and, to be honest, they just wanted a few hours outside the Mill and an easy stroll. I plotted it on a 20 thou map and saw that it was on the top of a mountain. Ah, I thought, they want to be dropped off on Slieve Gullian, so that's where they went. Hours later, I wandered into the mill to find a bit of a rumpus going on. The patrol was overdue. How could that be, said the watchkeeper, they were dropped off on Camlough, so it was only a couple of miles downhill.
Without saying anything, I made myself scarce, dug out the map, unfolded it and, yep, the grid reference was actually on the top of Camlough. Oops.
Much later that evening, they arrived back, knackered. The CO was convinced I had done it deliberately, but it really was an honest mistake.