In reply to Zygoticgema:
I had one who sounds similar. He was overqualified, and bored, but I pointed out that I could only give him more interesting work if he finished the dull stuff which needed doing. On the other hand, I have had admins who were equally bright, but appreciated that they had taken on the job, and took pride in doing it well.
The best was actually a guy who had only worked as a labourer before. I had to explain the absolute basics to him, but he was prompt and conscientious and never needed anything explaining twice. Brilliant.