Martin P-L writes:

His is the first name in the family bible.

Until his father's death, in 1838, he lived at Broom-(or Bloom-)field, which his mother left him.  The Oxon archive PL xviii/29 gives an account of his father's estate, on which H.P. had to pay much Land Tax - nearly £2,000 just for lands in Goring.

1817 He first married Julia Barrington, at Calbourne on the Isle of Wight, who died young, but not before bearing Philip Lybbe P-L and bequeathing many grand - particularly Plantaganet - quarterings.
She was descended from Sir Thos. Barrington, who married the Hon. Winifred Pole c. 1586.
Winifred was co-heir to Henry Baron Montagu, K.G., eldest son of Blessed Princess Margaret, the last of the Plantaganets.  Her father, George Duke of Clarence, was brother to Edward IV and Richard III, and was executed for treason.  Her brother, Edward Earl of Warwick (the last male Plantaganet) was beheaded on Tower Hill.  So was she.
(TFPL: Richard Pole, in this tree, was the half-first-cousin of Henry VII by his maternal grand-mother's second marriage to John Beaufort.)

             Richard, Duke of York
       _______|______________________________
      |               |                      |
Edward IV    George, Duke of Clarence      Richard III
              ______ |_____________
             |                     |
Edward, Earl of Warwick        Margaret = Sir Richard Pole
                                        |
c.1586         Sir Thos. Barrington = Winifred, 2nd daughter
                                     |
                            several generations
                                     |
c.1800                     Julia Barrington

She was buried in the (? a new) family vault, in the churchyard at Whitchurch.

TFPL: He married Philippa Cunliffe Shawe in 1823 and had a further 11 children, the first eight at his in-law's house, Southgate, (or might it have been Broomfield House, Southgate?) the last three at Hardwick.

TFPL: Henry Poole (or Pole) was not KG, though his father Richard was.

TFPL, Aug 2002: On 20 Jan 1846, he. HPP, was appointed deputy lieutenant of Oxon by the duke of Mrlborough; we still have the deed for this appointment with the Marlborough seal and signature.

TFPL, 1999: In the 1841 and 1851 censuses, there were enormous households at Hardwick (the name abbreviations are from the census abstracts I've got):

1841 first (Surname, Forename, Age, Occupation, Born in County)
  POWYS, Henry, 49, Ind, n
  POWYS, Phillippa, 39, , n
  POWYS, Louisa, 75, , n
  POWYS, Louisa Phill, 16, , n
  POWYS, Edward Shawe, 15, , n
  POWYS, Charles Rich, 13, , n
  POWYS, Fanny Mary A, 11, , n
  POWYS, Francis Arth, 10, , n
  POWYS, Isabella Lyb, 8, , n
  POWYS, Sophia Jane, 6, , n
  POWYS, Millicent Ca, 3, , n
  POWYS, George, 2, , y
  POWYS, Emma Charlot, 1, , y
  POWYS, William Conl, 4m, , y
  GILLISPEY, Janette, 30,
  WRIGHT, Harriott, 37,
  WHITE, Mary, 40, FS, n
  WHITE, Eliza, 28, FS, n
  WELLS, Mary, 30, FS, n
  HAWKINS, Mary, 28, FS, n
  ILLBERY, Ellen, 26, FS, y
  HARPER, Mary, 24, FS, n
  CURTIS, Mary, 18, FS, n
  PYGLER, Ann, 18, FS, y
  BROWN, Ann, 18, FS, n
  PLATER, James, 20, MS, n
  POCOCK, Jessey, 25, MS, n
  WAKELIN, James, 20, MS, n
  GLASCOCK, George, 18, MS, n
  SHAWE, Phillippa, 86?, Ind, n
  SHAWE, Mary Green?, 15, , n
  SHAWE, Emily Pole, 8, , n
  SHAWE, Henry Conlif, 6, , n
  BELLINGER, Elizabeth, 50, FS, n
  DUNDRIDGE, Ann, 40, FS, n

1851 census  (Surname, Forename, Relation, Married, Age, Occupation, Birth County & Parish)

  POWYS, Henry Philip, HD, m, 59, Magistrate & Landed Proprietor, OXF, Culham
  POWYS, Phillippa E, WI, m, 49, , MDX, Southgate
  POWYS, Louisa P, DA, u, 26, , MDX, Southgate
  POWYS, Frances M, DA, u , 21, , MDX, Southgate
  POWYS, Isabella L, DA, u, 18, , MDX, Southgate
  POWYS, Sophia J, DA, u , 18, , MDX, Southgate
  POWYS, Millicent C, DA, u, 13, , MDX, Southgate
  POWYS, Emma C, DA, u, 11, , MDX, Southgate
  PHILLIPS, Augusta E, NC, u, 28, , OXF, Cullum
  MORGAN, Frances, , u, 33, Governess, SOM, Bath
  WHITE, Elizabeth, SV, u, 39, Lady's Maid, MDX, London
  CHAPMAN, Harriet, SV, u, 28, Cook, OXF, Charlbury
  HEWLETT, Julia, SV, u, 34, Laundress, OXF, Oxford
  PRESTON, Eliza, SV, u, 27, House Maid, BRK, Wantage
  ILLBURY, Sarah, SV, u, 19, Under Housemaid, OXF, Goring
  EVANS, Charlotte, SV, u, 20, Kitchen Maid, OXF, Mapledurham
  LEWENDON, Ellen, SV, u, 17, School Room Maid, OXF, Whitchurch
  GLASSCOCK, George, SV, u, 27, Upper Footman, MDX, Edmonton
  PATEY, Benjamin, SV, u, 37, Coachman, OXF, Cullum
  HORNE, Jno, SV, u, 18, Footman, BKM, Fawley
  LEWENDEN, Jno, SV, u, 19, Groom, OXF, Whitchurch
  BROWN, Fredrick, SV, u, 12, Boy, OXF, Goring

Statistics

Census Yr   No in Family   Servants

  1841            18          17
  1851             8          14
_______________________________________________________________

Presumably it was he that was involved in the law suits of Powys v. Blagrave, reported in The Times (by Palmer's Index) on:
3 Nov 1853, p. 9, col a
23 Feb 1854, p. 12, col a
27 Feb 1854, p. 11, col. e
27 July 1854, p.11, col d
7 Aug 1854, p.8, col e

TFPL, Aug: 2002: I have just discovered some papers of that time with Blagrave Trust on them: to be looked at.
_____________________________________________________________

He wrote to The Times (ex Palmer's Index):
on 21 Oct 1834, on the Licensing the Cherry Tree, p. 3, col a
on 29 Oct 1834, on the same subject, p. 4, col. b.
on 17 Sep 1845, on The New Poor Law, p. 6, col. f,
on 22 Nov 1851 on Railway Grievance, p. 4, col. f.
_________________________________________________________________

In 1855 an income and expenditure statement was prepared for Hardwick:

Income:
Misc: 6640
Rent, G & B: 2547
Rent, Middx: 3232
Bec, tithes: 380
Dividends: 4245
Timber: 1411
Farm: 1502
Gravel: 1629

Total: 21,586

Expenditure
Household: 5183
Education: 958
Allowances: 2122
Wages: 562
Misc: 4034
Rates: 830
Timber: 620
Farm: 1252
Farm labour: 664
Garden stables: 475
Carpenters, etc: 129
Estate repairs: 119
Game: 253
Gravel: 772

Total: 17,844

Surplus of income over expenditure: 3,742
(for taxes, travel, clothes, etc)
________________

His death certificate give the cause as: Disease of Stomach 5 months.  The Informant was Martha (?) Ann White of Hardwick House, present at the death.
________________

From the London Gazette:

27 Jan 1846:  Commissions signed by the Lord Lieutenant of the County of Oxford.
John Sidney North, Esq. to be Deputy Lieutenant. Dated 20th January 1846.
William Peere "Williams Freeman, Esq. to be ditto. Dated 20th January 1846.
Henry Philip Powys, Esq. to be ditto. Dated 20th January 1846.
  We still have the signed appointment deed, by the duke of Marlborough.

14 Nov 1851: Appointed second Sheriff of Oxon.

16 November 1852: Appointed first Sheriff of Oxon.
_______________

Caroline Powys wrote in her diaries on 24th Nov 1801: Henry Powys Birth day born 1791.

I wonder if he was born in Culham, Berks?  This is what is on the enumerator’s sheet for the 1851 census.  Undoubtedly his maternal grandfather had owned Culham Court but that was inherited by his mother’s elder sister, Charlotte, who might well have been living there as she did not die until 1795.  No other source for his birth place.
_______________

His will not yet found: it was probably one of the first to be handled by the Probate Court at Holborn.
_______________

From “Office-Holders in Modern Britain: Volume 11 (Revised), Court Officers, 1660-1837”, pp. 1327-1384.

“Powys, Henry Philip Clerk of the Cheque of the Gentlemen Pensioners 10 Feb. 1813 (HO 38/15, pp. 314-15). Vac. by 28 Sept. 1815 (HO 38/17, p. 155).”
________________

TFPL, Jul 2018:  I have found this curious transcript on FamilySearch which has to be wrong in a few details:

Henry Philip Lybbe
England Births and Christenings, 1538-1975
Name: Henry Philip Lybbe
Residence Place: Wargrave, Berkshire, England
Gender: Male
Christening Date: 02 Jan 1792
Christening Date (Original): 2 Jan 1792
Christening Place: Wargrave, Berkshire, England
Father's Name: Philip Lybbe
Mother's Name: Louisa Michell Powys

Now to try to get a copy of an image of the actual baptism register.

Berks Record Office has the parish as “Wargrave St Mary”.

BUT...
The Berkshire FHS has also transcribed the Wargrave registers and have this entry instead:

First name(s) Henry Philip
Last name Powys
Baptism year 1792
Baptism date 02 Jan 1792
Place Wargrave
Church St Mary
Child's other details [Born] 24 Nov 1791
Relationship son of
Father's first name Philip Lybbe
Father's last name Powys
Mother's first name Louisa
Mother's last name Powys
County Berkshire
Country England
Record set Berkshire Baptisms Index

The interesting thing is that Family Search has Louisa the mother down with the name, correctly, of Michell.  Where did they get this from?  I still think the only resolution is in sight of the register page.

If, as it seems, FamilySearch have made a real mess of this, I wonder how one can tell them of the error?

Family Search have made a mess.  The first two entries on the first page for 1792 are:

Jan 2nd: Henry Philip Son of Philip Lybbe & Louisa Powys (late Louisa Michell) born November ye 24th 1791.

8 [Jan]: Henry Son of James & Elizabeth Chapman.

The reason for including the second entry is to show the syntax of these entries.  The parents are names as Forename(s) of father, Forename of mother, Surname of both.  The transcriber for Family Search had not noticed this syntax: incompetence!

I reported this as a problem to the Family Search website on Tues 24th 2018.
_______________

In the church of St Mary the Virgin, Whitchurch on Thames, Oxon

On top row on north side of Vault, in the churchyard:
  In memory of Henry Philip Powys of Hardwick
  who departed this life April 1st 1859 Aged 67 years.

Marriage register signed by H P P, J B, her father Fitzwilliam B., her unmarried sister Jane Elizabeth B. and some other Barrington whose forename(s) I cannot decipher.

From the Morning Post of Friday 17th October 1823, page 4:

“MARRIED--On Thursday, at St George’s Hanover Square, by the Rev Richard Powys, Henry Philip Powys., eldest son of Philip Lybbe Powys, Esq., of Hardwick House, Oxfordshire; and Broomfield House, Middlesex, to Philippa Emma Shawe, of Upper Brook Street, youngest daughter of the late Wm Cunliffe Shawe, Esq.”
_______________