45-46 looks like a nursing home. Search by Address.
He is there.
I can't give you more info as it's the 1921.
Following Gadget's and Hanes Replies
1926
This example referring to the Inquest of the Late Mrs M. E. Lloyd:-
"
She was removed on October 14th to a Nursing Home at 45, Devonshire-street, Marylebone."
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You may have seen this already ...
2/Lieutenant Ronald Vanstone MILLARD. General List.
The National Archives, Kew, Cat. Ref:
WO 374/47711
Date 1918 to 1921
Former Departmental Reference: 1375
https://discovery.nationalarchives.gov.uk/details/r/C717839 ---------------
Births and Deaths Registration Act 1874
https://www.legislation.gov.uk/ukpga/Vict/37-38/88/body/enacted/data.htm?view=plain10. Information concerning death where deceased dies in a house
"
When a person dies in a house after the commencement of this Act, it shall be the duty of the nearest relatives of the deceased present at the death, or in attendance during the last illness of the deceased, and in default of such relatives, of every other relative of the deceased dwelling or being in the same sub-district as the deceased, and in default of such relatives, of each person present at the death, and of the occupier of the house in which, to his knowledge, the death took place, and in default of the persons herein-before in this section mentioned, of each inmate of such house, and of the person causing the body of the deceased person to be buried, to give, to the best of his knowledge and belief, to the registrar, within the five days next following the day of such death, information of the particulars required to be registered concerning such death, and in the presence of the registrar to sign the register."
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This suggests a Funeral Director, or a person taking charge of the body for burial can also be the Informant.
ADDED:
Was he buried in England, or Canada?
A long time ago, I researched a crash of a Lockheed Hudson aircraft in England in 1940.
The family in Canada of the Captain had authorised a friend 'Representative' in England to go and claim his coffin waiting in the church for burial from the Air Ministry. Instructions were then given to a Funeral Director in England to collect his coffin and prepare him for repatriation to a Funeral Home in Canada for burial there.
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ADDED:
A Local Authority currently says:-
A qualified informant is:
a relative by blood, marriage or adoption of the person who has died
the partner of the person who has died
a person who is not related but was present at the death
a person who is arranging the funeral
an occupier of a building such as a care or nursing home manager
the personal representative of the deceased i.e. someone appointed by them or their family such as a Solicitor