A friend who was a lecturer at St Andrews was a keen member of the Territorial Army. His regiment was the Black Watch, and he told me of how he came to obtain his commission. Shown into the colonel's office for his interview, he was invited to pour himself a drink from the cabinet at the side. He picked up the whisky decanter and sought the delicate balance between pouring too little and being thought a wimp, or pouring too much and being thought a soak.
As he was pouring, the colonel distracted him with a conversation, and my friend realized to his horror that he'd accidently filled his tumbler to the brim with neat whisky. He carefully covered the glass with his hands, sipping occasionally as the interview went on. Eventually he managed to get through all of it. The interview was successful and he was awarded the commission. He later learned that the colonel had called in his fellow officers and told them, "It's got to be Jackson. Chap drinks like a fish!" This was sometimes how officers were recruited.