In 1655 [his mother] Anne Mordaunt died.

In 1668 [his father] Giles Estcourt 1st Baronet died. His son [his brother] Giles Estcourt 2nd Baronet (age 13) succeeded 2nd Baronet Estcourt of Newton in Wiltshire.

Before 20 Nov 1684 William Estcourt 3rd Baronet (age 30) served as foreman of the jury which acquitted Edward Nosworthy (age 46). During the course of the celebrations that followed in the Globe Tavern, Fleet Street an altercation broke out between Henry St John 1st Viscount St John (age 32) and Francis Stonehouse (age 31). William Estcourt 3rd Baronet (age 30) was killed by either or both Henry St John 1st Viscount St John (age 32) and Francis Stonehouse (age 31). Both were fined and pardoned. Baronet Estcourt of Newton in Wiltshire extinct.