William Longsword, 3rd earl of Salisbury, Longsword also called Longespée, (died March 7, 1226, Salisbury, Wiltshire, England), an illegitimate son of Henry II of England who became a prominent baron, soldier, and administrator under Kings John and Henry III. His date of birth is not known, and his parentage was, for many centuries, a mystery. He was long assumed to have been the son of Rosamond, with whom Henry II had an infamous affair. By the early 21st century, however, documents had been discovered that indicated that his mother was probably Countess Ida de Tosny, who later married Roger Bigod,