A quick Google brought up another sighting of Percival Tring this time, again from National Archives, relating to the will of Thomas Tring, the elder, of Leighton Buzzard dated 16 Nov 1759, where he leaves property to his son Thomas Tring, but if he don't want it then they go to son Percival Tring, & following on after to Percival's daughter Rebecca.
So how do you think Percival's parents were John Tring & Sarah Tuley ?
Cheers John