Tom Hayes was sitting at his kitchen table with his father one weekend this March, surrounded by piles of legal documents and sipping from a can of Coke. Nick Hayes usually scolded his son for drinking Coke, but this day he let it slide. He had another point to make.

If the younger Hayes had gone through with his original plan to plead guilty to charges that he manipulated Libor, his father noted, his prison sentence would be just about over.