His birth in Oz from FindMypast’s transcript:

First name(s)        Robert John
Registration number  9026
Last name            Hennell
State                Victoria
Sex                  Male
Country              Australia
Birth year           1872
Record set           Victoria Births
Birth place          Geelong
Category             Birth, Marriage, Death & Parish Records
Father's name        Charles Orton
Subcategory          Civil Births
Mother's name        Maria Jane
Collections from     Australasia, Australia
Mother's last name   Huelin
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In his 1911 census, Gladys bweing with her mother, he stated he had been married for 2 years and had no children and they were at 45 Upperton Gardens Eastbourne, Susse:

                                Marital
First name(s)  Last name  Role  status  Sex  Age  Birth year  Occupation  Birth place
Maria Jane   Hennell  Head  W  F  65  1846  Private means    Jersey Resident
Robert John  Hennell  Son   M  M  39  1872  Private means    Victoria Australia Resident
Annie        Button   Serv  S  F  23  1888  General servant  Eastbourne Sussex

1911 ref: RG14PN4835 RG78PN208 RD71 SD2 ED23 SN25
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His death index:

Name:                     Age at Death (in years):  
HENNELL, ROBERT JOHN      76  
GRO Reference: 1948  D Quarter in EASTBOURNE  Volume 05H  Page 221
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His probate index:

1949
HENNELL Robert John of Roma Willingdon Sussex died 9 December 1948 at The Esperance Nursing Home Eastbourne  Probate Lewes 9 February to Gladys Margaret Powys Hennell widow and Charles James Hennell export clerk.  Effects £6032 14s.

Will ordered.  Done on 22nd March 2022.
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His probate added that there were two codicils to the will and that Charles James Hennell was of 40 Elmwood Welwyn garden City Hertfordshire and a son of the deceased.
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His will was dated the thirteenth day of March 1939 and the two codicils were dated 28th May 1940 and Febr. 24th 1947.  In it he listed these relatives:

1. His wife Gladys Margaret Powys Hennell,
2. His son Charles James Hennell,
3. His sister-in-law Elsie Kathleen Mary McGee of 589 Jarvis Street, Toronto, Canada,
4. His sister-in-law Ethel Louisa Powys Drummond, then in India,
5. His sister-in-law Eileen Amy Powys Hughes of 1 Circus Road mansions St Johns Wood N.W.8,
6. His wife’s aunt Edith Raven-hart of 4 Spencer House Larkhall S.W.8,
7. His brother-in-law Leopold Douglas Bell Drummond of Fulford harbour British Columbia, Canada,
8. His brother-in-law’s wife Mary Elizabeth Drummond,
9. His brother-in-law Major James Geoffery Powys Drummond M.C. of 156 Pinner Road Oxhey Watford Herts,
10. Miss Violet Vyse of 8 Circus Road Mansions, St Johns Wood, N.W.8
11. Miss ASileen Vyse of the same address,
12. Mrs Dunstall of Myrtle Cottage Wish Hill Willington
13. The children of Mrs Dunstall, Mrs Minni Britton and Miss Phyllis Dunstall,
14. Mrs Flaxman of 46 Freeman Avenue Hampden Park Eastbourne,
15, Miss Crawley of 32 Bedford Grove Eastbourne.

I am not usre if his estate would have funded all those bequests if his wife pre-deceased him.

No surprises in the above apart from his wife’s aunt, Edith Raven-Hart, who is not found among the  Powys descendant aunts but may be an aunt on her mother’s Fairbrother side, which I have not been following.
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Theri marriage index:

First name(s)     Gladys Margaret P
Last name         Drummond
Marriage quarter  4
Marriage year     1908
Marriage Finder   Gladys Margaret P Drummond married one of these people
                  Robert John Hennell
District          East Grinstead
County            Sussex
Country           England
Volume            2B
Page number       279
Record set        England & Wales Marriages 1837-2005
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