No record can be found of his birth or baptism.

But, January 2021, TFPL: his baptism transcription from the Register image:

Place:             Parish of St George, Bloomsbury, Middlesex
Year:              1848
Date batised:      June 6
Date born:         Feb 1
No:                358
Name:              Evelyn Archer [Powys]
Parents            Bransby William and Catherine Blick
Surname:           Powys
Abode:             Guilford Street
Father’s job:      Solicitor
Officaiting Minr:  Arthur W???????????
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Shrewsbury School records says only: ‘Ranching, Mathravel, Menteith, P.O., Manitoba.
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This is probably his immigration to Canada:

Name:            E.(Mr) POWYS
Year of Record:  1886
Source/Event:    Passenger List: Port of Halifax
Comments:        Arrived on the 'Peruvian'
Age:             32
Reference:       National Archives of Canada: Microfilm Reel No. C-4513 page 6

But, below, on 15 Sep 1885 he acquired 139 acres in Manitoba, Canada.
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I wonder if he had anything to do with an Ernest Aubrey Powys whose son Edmond Ivor Owen was killed in WW1.  From the Commonwealth War Graves Commission site (www.cwgc.org):

Name: POWYS, EDMOND IVOR OWEN
Initials: E I O
Nationality: Canadian
Rank: Private
Regiment: Canadian Infantry (British Columbia Regiment)
Unit Text: 29th Bn.
Age: 20
Date of Death: 19/08/1917
Service No: 790894
Additional information: Son of Ernest Aubrey and Margaret Annie Powys, of 1264, 11th Avenue, New Westminster, British Columbia.
Casualty Type: Commonwealth War Dead
Cemetery: VIMY MEMORIAL

Subsequent note in Dec 2012: The recent release by the Royal British Colombia Museum of many birth, marriage and death records including images of a majority of the certificates, has solved this mystery.  Ernest Aubrey Powys was born in Sydney, Australia and was the son of Robert Owen Powys and Emma Jane, née Smith.  So far no relationship is conjectured with the descendants of William Powys of Ludlow (d. 1577).
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In 1871 he was a Solicitor’s General Clerk living with his father in Bloomsbury.  Born in St Georges Bloomsbury, Middlesex.
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He applied for and obtained a series of land grants in Canada:

15 Sep 1885: He was of Township seven, Range 22 West of the Principal Meridian, Manitoba and a farmer, granted 139 acres.
16 July 1887: Same address, farmer, granted 160 acres.
15 Jul 1891: Of Soulis, Co Branton, Manitoba, farmer, granted 160 acres.
8 Jun 1892: Of Brandon town, Co Brandon, Manitoba, Clerk, granted 160 acres.
24 Oct 1893: He was of Menteith, Manitoba and a farmer, granted 160 acres.

Looks like a total of 779 acres.  Plus the land he was farming when he got his first grant.

Obviously he was alive during the Canadian 1891 census, yet he is not to be found on that at all.  Nor is he to be found on the 1901 census.
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Nov 2010, TFPL: I have yet to find any record of his death or of his will.  Manitoba has no public access to any of its records, in complete contrast to BC.
Update in 2020, TFPL: Manitoba now has public access to old records but I can find no death records for anyone with the surname of POWYS.
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