Her birth index:

First name(s)         Lucinda M S
Last name             Sackville
Birth quarter         4
Birth year            1963
Mother's maiden name  Coles
District              Westminster
County                London
Country               England
Volume                5C
Page                  356
Record set            England & Wales Births 1837-2006
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This looks very strongly to be her death, if only because the births coincide:

First name(s)               Lucinda Mary
Last name                   Stopford-Sackville
Gender                      Female
Birth day                   15
Birth month                 10
Birth year                  1963
Death quarter               1
Registration Month          2
Death year                  1993
District                    Cambridge
District number             3311A
Register number             A34C
Entry number                256
Date of registration mm/yy  0293
County                      Cambridgeshire
Country                     England
Record set                  England & Wales Deaths 1837-2007
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Her early death is said to have been in a motor smash.
___________________

Her probate index:

1993
SACKVILLE, Lucinda mary Stopford-
of 2 Lowther St, Newmarket Suffolk
Died 26 November 1992  Administration London 10 February
£171496 9351103835X