Two birth index entries found for FindMyPast’s World records:

                          Year of
Last name  First name(s)  Birth   Record set                        Location
O'Farrell  George C       1917    England & Wales Births 1837-2006  Steyning, Sussex
O'Farrell  George C       1936    Irish Births 1864-1958            Dublin South, Dublin, Ireland

I would guess the second but it could as easily be the first of these.
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In 1939, there is no George C Farrell and this plain George does not fit in with either of the above two birth years, at Saint Vincents Orthopaedic Hospital Wiltshire Lane Eastcote, Pinner, Ruislip, Ruislip-Northwood U.D., Middlesex:

First name(s)        George
Last name(s)         O'Farrell
Birth date           08 Jun 1921
Birth day            8
Birth month          6
Birth year           1921
Sex                  Male
Marital status       Single
Institutional role   Servant
Occupation           Gardeners Company
Schedule             4
Schedule sub number  187
  
Archive reference RG101/0875F/007/30
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His second forename of Croker is known from the will of his father-in-law.
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Their marriage index:

First name(s)       Anne P
Last name           Scott
Marriage quarter    3
Marriage year       1948
Marriage Finder     Anne P Scott married one of these people
                    George C O'Farrell
Spouse's last name  O'Farrell
District            Banbury
County              Oxfordshire
Country             England
Volume              6B
Page number         2121
Record set          England & Wales Marriages 1837-2005
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