Question: Who is the paternal grandfather of John Tuchet, 8Th Earl Of Castlehaven?

Knowledge 1: John Tuchet, 8th Earl of Castlehaven
John Talbot Tuchet, 8th Earl of Castlehaven (2 August 1724 – 22 April 1777) was the son of James Tuchet, 6th Earl of Castlehaven, and his wife, née Elizabeth Arundell.He succeeded his brother as Earl of Castlehaven and Baron Audley on 6 May 1769.He died unmarried, at which time the Earldom of Castlehaven and two of its subsidiary titles (Baron Audley of Orier and Baron Audley of Hely) became extinct as the Irish earldom and baronies were entailed honours.The Barony of Audley created by writ of 1312 is deemed to have devolved upon his nephew, namely George Thicknesse (later Thicknesse-Touchet).George was the son of his sister Elizabeth, who had married Philip Thicknesse [SEP] Knowledge 2: James Tuchet, 6th Earl of Castlehaven
James Tuchet, 6th Earl of Castlehaven (died 12 October 1740) was the son of James Tuchet, 5th Earl of Castlehaven and his wife Anne Pelson.He succeeded his father as Earl of Castlehaven and Baron Audley on 9 August 1700.He married, on 14 May 1722, Elizabeth Arundell (1693–1743), daughter of Henry Arundell, 5th Baron Arundell of Wardour and his wife, née Elizabeth Panton.They had two sons, and at least one daughter:He is buried at the church of St. Sulpice in Paris, France.
Knowledge 1: John Tuchet, 8th Earl of Castlehaven
John Talbot Tuchet, 8th Earl of Castlehaven (2 August 1724 – 22 April 1777) was the son of James Tuchet, 6th Earl of Castlehaven, and his wife, née Elizabeth Arundell.He succeeded his brother as Earl of Castlehaven and Baron Audley on 6 May 1769.He died unmarried, at which time the Earldom of Castlehaven and two of its subsidiary titles (Baron Audley of Orier and Baron Audley of Hely) became extinct as the Irish earldom and baronies were entailed honours.The Barony of Audley created by writ of 1312 is deemed to have devolved upon his nephew, namely George Thicknesse (later Thicknesse-Touchet).George was the son of his sister Elizabeth, who had married Philip Thicknesse [SEP] Knowledge 2: John Tuchet, 4th Baron Audley
John Tuchet, 4th Baron Audley, 1st Baron Tuchet (23 April 1371 – 19 December 1408) was an English peer.John Tuchet, 4th Baron Audley was the son of Sir John Tuchet, called "Baron Audley", and his wife Maud, widow of Sir Richard de Willoughby.His paternal grandparents were Sir John Tuchet (1327—1371) and his wife Joan Audley (1331–1393, daughter of James Audley, 2nd Baron Audley and first wife Lady Joan Mortimer).In 1391, when his childless great-uncle Nicholas Audley, 3rd Baron Audley died, the Audley Barony was abeyant.Meanwhile, he was created 1st Baron Tuchet in 1403 and received one-third of the share of the barony of Audley.In 1408 the Barony was revived, and John Tuchet became 4th Baron Audley.
Before 1398, he married Elizabeth Stafford, daughter of Sir Humphrey Stafford and his first wife, Alice Grenville.They had one son, James, and two daughters, Margaret and Elizabeth.John was succeeded by his only son, James Tuchet.
Knowledge 1: James Tuchet, 6th Earl of Castlehaven
James Tuchet, 6th Earl of Castlehaven (died 12 October 1740) was the son of James Tuchet, 5th Earl of Castlehaven and his wife Anne Pelson.He succeeded his father as Earl of Castlehaven and Baron Audley on 9 August 1700.He married, on 14 May 1722, Elizabeth Arundell (1693–1743), daughter of Henry Arundell, 5th Baron Arundell of Wardour and his wife, née Elizabeth Panton.They had two sons, and at least one daughter:He is buried at the church of St. Sulpice in Paris, France. [SEP] Knowledge 2: John Tuchet, 4th Baron Audley
John Tuchet, 4th Baron Audley, 1st Baron Tuchet (23 April 1371 – 19 December 1408) was an English peer.John Tuchet, 4th Baron Audley was the son of Sir John Tuchet, called "Baron Audley", and his wife Maud, widow of Sir Richard de Willoughby.His paternal grandparents were Sir John Tuchet (1327—1371) and his wife Joan Audley (1331–1393, daughter of James Audley, 2nd Baron Audley and first wife Lady Joan Mortimer).In 1391, when his childless great-uncle Nicholas Audley, 3rd Baron Audley died, the Audley Barony was abeyant.Meanwhile, he was created 1st Baron Tuchet in 1403 and received one-third of the share of the barony of Audley.In 1408 the Barony was revived, and John Tuchet became 4th Baron Audley.
Before 1398, he married Elizabeth Stafford, daughter of Sir Humphrey Stafford and his first wife, Alice Grenville.They had one son, James, and two daughters, Margaret and Elizabeth.John was succeeded by his only son, James Tuchet.

Answer: James Tuchet, 5th Earl of Castlehaven