Yep, I well remember a dusk drop on the Scots coast, back in the 1970's.
After clearing the DZ and 'rallying' at the edge of a wood, a young subaltern 'took charge' and lead my patrol along a narrow road to a 'T' junction, and turned right. Being a relatively young, but fairly experienced Para at the time, I didn't question this officer's actions at first, until we'd gone around two or three miles, with the setting sun behind us.
At this point, I politely asked said 'officer' what route he was taking to the Btn RV, whereupon he showed me on his map, with the his compass in hand too.
A quick glance showed he'd committed the mortal sin of transposing the Grid Reference numbers and, not only was he one square mile 'out' when setting off, he was heading in the opposite direction to that needed to reach the RV, having read his compass bearing as Magnetic, without converting to 'Grid', and back to front to boot (i.e a full 180 degrees out)!!
A brief comment on his heritage, a call to the lads, and, with my map in hand, we ran in the opposite direction, arriving at the RV on time, but with a very knackered and red-faced Subaltern in tow !
For some reason, we never saw that officer again ..................