William was the descendant of the de Parles family of Hounesworth (Handsworth) in Staffordshire, one of the counties of the West Midlands. He became the husband of Joan de Watford, the third of four daughters of Eustace, the Lord of Watford. In accordance with his obligation as the holder in right of his wife of a quarter knight's fee, he served as a knight in the king's war against the Welsh in July 1277.
In 1278, a certain sir Philip, son of Robert, was murdered. Soon after, William de Parles was arrested for the felony. The trial was conducted by sir Ellis de Hauville. William was found guilty and hung for the crime in November 1278. As a result of his 'crime', William's own lands were stripped from him and granted to someone else.
A year and a half later, the children of William de Parles formally petitioned King Edward I and his council. This was done in writing in medieval French, the language of the Norman kings (see transcript, The Watford Knight's Fee, page 117). They asked that pity be taken of them for the wrong done to their father in the false accusation of murder, and that William's lands be returned to them. They explained that the king had instructed sir Ellis to refer to the king before any action was taken, no matter what the outcome of the trial. But sir Ellis ignored the order in contempt of the king. Since then, they said, others had been arrested and were held in Newgate prison for the crime, and had even admitted guilt. The king and council remained unmoved, noting: 'Nothing is to be done for them.'
Nonetheless, although William's widow and children lost the lands William had held of his own right, including Handsworth and Great Rollendrich, they retained the lands William had held in right of his wife, because she was one of the four heirs of Eustace de Watford IV.