This birth of a J M Macdonald was found on FreeBMD:

Surname First name(s) District Vol Page
Births Dec 1905   (>99%)
Westwood John Macdonald Hackney 1b 369
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And if the above was his birth, here’s his parents and he in in the 1911 census:

Name Relation Condition/ Yrs married Sex Age Birth Year  Occupation  Where Born

WESTWOOD, John Head Married M 46 1865 Private Secretary in Tea and Provision Business  Fifeshire, Dunfermline
WESTWOOD, Patience Jane Wife Married  9 years F 30  1881  Lancashire, Southport
WESTWOOD, Marjorie Daughter F 7 1904 London, Finsbury Park
WESTWOOD, John Macdonald Son M 5 1906 London, Finsbury Park
MACDONALD, Emmie Sister In Law Single F 24 1887   Hospital Dispenser  Lancashire, Southport

RG number: RG14 Piece: 7384
Reference: RG14PN7384 RG78PN357 RD132 SD5 ED34 SN311

Registration District: Edmonton   Sub District: Edmonton
Enumeration District: 34 Parish: Southgate

Address: 17 Haslemere Road Winchmore Hill N
County: Middlesex

And the sister-in-law establishes that Patience’s maiden name was macdonald, accounting for the use of that name for their son John.
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In 1948 he was on a boat to Ceylon:

First name(s) John Macdonald
Last name Westwood
Title MR
Gender Female  [ sic! ]
Age 42
Birth year 1906
Occupation CO DIRECTOR
Departure year 1948
Departure day 7
Departure month 8
Departure port Liverpool
Destination port Colombo
Destination COLOMBO
Country Sri Lanka (Ceylon)
Destination country Sri Lanka (Ceylon)
Ship name Derbyshire
Ship official number 164273
Ship master's first name P H
Ship master's last name POTTER
Ship master's title CAPT
Shipping line BIBBY LINE
City LIVERPOOL
Ship destination port RANGOON
Ship destination country BURMA
Ship registered tonnage 10623
Number of passengers 120
Record set Passenger Lists Leaving Uk 1890-1960
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Possibly he died before 1975 as that is the date of Cynthia’s second marriage.

Yes, he was ‘deceased’ on the marriage certificate for his son in Feb 1973.  So died before Feb 1973.

Death not found on FindMypast’s ‘World’ database.

Nor any probate entry on the English probate index from 1959 to 2005.
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In the Times of 7 Nov 1939:

WESTWOOD : HALLIFAX.__On Nove 4, 1939 at St Peter’s Church, Colombo, Ceylon, John Macdonald Westwood, to Cynthia Margaret Hallifax.
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