Martin P-L writes:
Clerk of the Treasury: 1662-1723, brother of Sir Thomas.
He was one of the principal clerks of the Treasury (family MS book).
There are a few letters from him in the British Library.  One, written in 1707, lamented his imminent death from gout - but he lived for another 16 years.
There are other letters relating to him (termed fascinating by Mary Creaser) in the Shrewsbury Record Office.
References to him in the PRO (unread by me) are:-
10 William III (ie. 1698)  Exchequer Depositions  Mich./27  Salop.  Group 2.
1703  Chancery Proceedings,  Bridges 3/312.
There must be records of  him in the Treasury as well.
The transcription of Sir Littleton's papers includes: Elizabeth, wife of my brother Richard, dyed 22. 1. 1721.  From other sources the only wife we know of is Anne, daughter of John Singleton.  Their son Richard married Lady Brudenell, dau. of the Earl of Cardigan.  Their daughter, also Anne, married Thos. Hill MP of Fern Hall and Shrubstone Park.  The grandchildren continued this upward mobility, Richard's daughters marrying Viscount Sydney and the Earl of Courtown respectively, and Anne's son becoming the first Lord Berwick of Attingham.
Richard senior's will survives, PRO 1723, Bolton 41.  It instructed that he be buried in Hintlesham church, Suffolk.  (He had bought Hintlesham Hall). To Charles Cotes of Inner Temple and Andrew Hill of the Navy Office, all my lands in Suffolk for 99 years on trust.  To my son Richard the farm I bought in Caenham, Salop (which had previously belonged to his father and been farmed by his uncle Peter and his cousin -
Peter's son - Richard).   His mother was nee Cotes, so Charles Cotes was presumably a relation.  The Andrew Hill was presumably connected to the Hills who married his sister and daughter.
He had no male Powys grandchildren.

TFPL, May 2001: Miscellania Genealogica aet Heraldica, fifth series, Vol VII, p. 360 has a review of "Timperley of Hintlesham. A study of a Suffolk Family" by Sir Gerald H Ryan, Bt and Lilian J Redstone, pub by Methuen & Co of London at 8s and 6d, c,1930.  The review says that the Timperley's owned the manor from 1434 to 1720 when Richard Powys bought it and that "many alterations and additions were made to the original building after it came into the Powys family."  The book "has two pedigree tables".

In 1725, according to Alumni Oxoniensis, he was living at St Anne's Westminster.
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Shropshire Record Office has several reference to a J Slaney (Mrs?) being an aunt of Richard P.  Her son was Morton Slaney.
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Aug 2017, TFPL: In his will he gave £20 to the poor of Bitterley “where I was born”, which adds in that morsel of information.
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Aug 2017, TFPL:

The wording of his baptism entry from the image of the Bitterley register is, roughly:

“Anno Domy 1662
Baptizati
...
Richardus filius Thomae Powys Armg: per Mariam uxori baptizatus decimo qinter die Decembrie”

FindMyPast’s transcription incorrectly reads:

First name(s)           Richardus
Last name               Powys
Baptism year            1662
Baptism date            15 Dec 1662
Denomination            Anglican
Place                   Bitterley
Father's first name(s)  Thome
Mother's first name(s)  Armg [sic, should be Mariam]
County                  Shropshire
Register type           Composite
Register date range     1658-1715
Archive reference       P34/A/1/1
Page                    7
Record set              Shropshire Baptisms
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His burial transcription:

First name(s)  Richard
Last name      Powis
Death year     1724
Burial year    1724
Burial date    23 Feb 1724
Church         St Nicholas
Denomination   Anglican
Place          Hintlesham
County         Suffolk
Country        England
Record set     National Burial Index For England & Wales
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Will of Richard Powys of Saint Anne in Westminster, Middlesex 18 February 1724 PROB 11/595
    though the latin original says the probate date was “decius octavo die Mensis February Anno Domini ... Septingentismo Vicesimo Tertio” which indicates that the 1724 is the date in the modern Julian calendar.

The will was dated “ninth day of May One Thousand seven hundred twenty three in the Ninth year of the Reign of our Sovereign Lord King george of Great Britain”.
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Their marriage licence:

Last name          POWYS
Gender             Male
Licence year       1699
Licence date       04 Jan 1699
Groom's last name  POWYS
Bride's last name  SINGLETON
Place              Dioceses of the Province of Canterbury
Record set         Vicar General Marriage Licences
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