This is almost certainly the birth record for the female later known as Nina V Akroyd when she married John D M Arnold.  I have ordered her birth certificate from GRO to see who were her parents.  The birth index is:

First name(s)         Vina V        <——  This is misread from ‘Nina Vivian’
Last name             Akroyd
Birth quarter         3
Birth year            1941
Mother's maiden name  Stadd         <—-  I am expecting this to be ’Studd’ - which it was.
District              Eton
County                Buckinghamshire
Country               England
Volume                3A
Page                  2455
Record set            England & Wales Births 1837-2006

I may end up having to get a copy of the birth certificate from the District office if the one from the GRO still shows oddities.

Answer: The Birth certificate, delivered on 23rd April 2021, was misread by the GRO.  Her registered name was indeed Nina Vivian but the initial ’N’ had a faint upward stroke on its left so it was mistaken for a ‘V’.  I can put a ‘postem’ on Freebmd, but cannot do any such thing on FreeBMD as the index sheet was correctly transcribed into their records.  The error was by the person at the GRO who did the transcribing from the certificate they received to the indexes.  The GRO also mistranscribed the Studd maiden name of the mother.  I can report this to the GRO.
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From the birth certificate:

No:            223
Birth event:   Fifth September 1941  Fulmer Chase Fulmer R.D.
Name:          Nina Vivian
Sex:           Girl
Father:        Bayly Gilbey Akroyd
Mother:        Lavender Vivian Alnod Akroyd  formerly  Studd
Father’s job:  Captain Royal Corps of Signals (Wheat buyer) of The Orchard Cottage, Souchen End, Holyport, Berks
Informant:     Lavender Akroyd Mother  The Orchard Cottage, Souchen End, Holyport, Berks
Registered:    Tenth September 1941
Registrar:     F H Roberts
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The evidence that this is the record for the daughter of Lavender Vivian Alnod Akroyd whose maiden surname was Studd:

1. The above index entry is so close to the person named in her marriage and in her mother’s will,
2. At marriage she was named as Nina V Akrayd, very close to Akroyd,
3. On her mother’s will she was named as Nina V Akroyd,
4. On both the birth indices for her children, her maiden name is given as Akroyd,
5. On her mother’s will, her children were named as Annabel Louise Beach and Fiona Deidre Cline,
      where the forenames correspond to the children she and David John had
      plus the surnames from their subsequent documented marriages,
      BUT Fiona’s married name was incorrect on her grandmother’s will - it was Clive.

On the basis of this I am entering all of h, her husband and their children with her as the daughter of Lavender Akroyd.
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Her death index, confirmed by the identical birth date as on her birth certificate:

First name(s)               Nina Vivian
Last name                   Arnold
Gender                      Female
Birth day                   5
Birth month                 9
Birth year                  1941
Death quarter               1
Death year                  1996
District                    Tower Hamlets
District number             2461D
Register number             D32
Entry number                156
Date of registration mm/yy  0396
County                      London
Country                     England
Record set                  England & Wales Deaths 1837-2007
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Her probate index:

Surname  First name   Date of probate  Probate number  Date of death  Document type   Registry
ARNOLD   NINA VIVIAN  22 July 1996     9651115445      23 March 1996  Grant and will  London
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Their marriage index:

First name(s)       Nina V
Last name           Akrayd
Marriage quarter    2
Marriage year       1963
MarriageFinder      Nina V Akrayd married one of these people
                    David J Arnold
Spouse's last name  Arnold
District            Maidenhead
County              Berkshire
Country             England
Volume              6A
Page number         59
Record set          England & Wales Marriages 1837-2005
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