Her baptism register image, thanks FindMyPast, transcript by me:

“Baptisms solemnized at S Mary’s Church Camp Aden in the Diocese of Bombay
“. . . .
When Baptized:       “1882 May 6
Said to be Born:     “1882 April 8
Child’s Forename:    “Eileen Amy Powys
Sex:                 “Daughter of
Parents’ Forenames:  “Emily Katherine Elizabeth Mary & James Houlbrooke
Parents’ Surname:    “Drummond
Abode:               “Aden
Profession:          “Colonel, Bombay Staff Corps
Celebrant:           “W. Wingate, Chaplain

Interestingly to me, the forename of Powys had first been written as ‘Powis’ then firmly crossed out, the correct spelling written above with the initials of ‘w.W.’ , the Chaplain, beside.
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No children found so far.
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In 1939 they may have been lodgers at 1 Camden Crescent, Bath, Somerset:

                                                          Marital  Schedule
First name(s)  Last name(s)  Birth date  Sex  Occupation  status   Main  Sub
Hetty E     Reid      12 Dec 1864  F  Private Means           W    133  1
Ian D E     Hughes    10 Oct 1881  M  Civil Engineer Public Works Dept Punjab India Retd
                                                              M    133  2
Eileen A P  Hughes    08 Apr 1882  F  Unpaid Domestic Duties  M    133  3
Ivy M       Farthing  06 May 1909  F  Domestic Service        S    133  4

1939 ref: RG101/7005G/010/15
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Her death index, with the birth date agreeing with that at baptism and on her father’s pay records:

First name(s)  Eileen Amy P
Last name      Hughes
Gender         Female
Birth day      8
Birth month    4
Birth year     1882
Death quarter  1
Death year     1970
District       Hemel Hempstead
County         Hertfordshire
Volume         4B
Page           349
Country        England
Record set     England & Wales Deaths 1837-2007
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Her probate index:

1970
HUGHES Eileen Amy Powys of 31 Upper Highway Hunton Bridge Kings Langley Herts died 13 January 1970  Probate Ipswich 30 June 1970.  £54031.

Will ordered.
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In her probate it added that she died at General Hospital West Wing, Hemel hempstead, Hertfordshire and that her executors were Charles James Hennell export supervisor nephew and peter Robert Hennell salesman great nephew of the deceased, both of 24 Reddings Welwyn Garden City hertfordshire.
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In her will dated 19th October 1967 she had been living at Arian House, 31 Upper Highway, Hunton Bridge, Kings Langley, Hertfordshire,  She named:

1. Her nephew Charles James Hennell of 24 Reddings Welwyn garden City, Herts,
2. Her great nephew Peter Robert Hennell of the same address,
3. Her Brother Leopold Douglas Bell Drummond of Fulford harbour, British Columbia, Canada
4. Her brother’s wife Mary Elizabeth Drummond,
5. her sister-in-law, Mrs Elsie Drummond,
6. Her nephew Michael Drummond,
7. the wife of Michael, Doreen Drummond,
8, Her nephew Dav id Anthony Drummond,
9. Her great nephew peter Robert Hennell,
10. Mrs Joan Warren of White Lodge Framlingham Suffolk,
11. Mrs Mary Rose Haen-hart care of Barclays bank Limited Durban,
12. Mrs Ethel Beatrice Prother of 77 Wrens Avenue Ashford Surrey,
13. David Edward Gordon Prother, son of the late Edward Charles Prother and the late Evelyn Grace Prother,
14. Michael Ian Prother, brother of David Edward Gordon Prother,

This mimics the will of Robert John Hennell and has no genealogical surprises.
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Their marriage register page, thanks FindMyPast, transcript by me:

Marriages solemnized at Christ Church Lucknow
“. . . .
When Married
  Year       “1921
  Month:     “April
  Day:       “18

                 His                Hers
                 ===                ====
Forenames:   ”Ian David Erskine  Eileen Amy Powys
Surname:     “Hughes             Drummond
Age:         “39                 39
Condition:   “Widower            Spinster
Profession:  “Civil Engineer     -
Residence:   “Sarghada           Lucknow
Father:      “A.B.M.Hughes       J. H. Drummond

Bann/Lic:       License
Couple Sigs:    I.D.E. Hughes, Eileen.A.P.Drummond
Witness Sigs:   E.S.P.Drummond, J.G.P.Drummond
Celebrant Sig:  W.R.O.S.Bennet
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