For a very useful overview see -
https://www.asc.ox.ac.uk/sites/default/files/2024-07/AllSoulsCollegeChapelGuide.pdf
Radclyffe Howard.
1768.
Suggested here as sculpted in the workshop of Robert Taylor.
Facing one another across the outer chapel.
The monuments of the Architect George Clarke and Dodington Grevile (a Tory parliamentarian opposed to the extension of religious toleration who helped with funding).

Releif of Dodington Grevile
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The Mural Monument of Marow Knightly.
inscribed aged 20, died 1731.
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The Mural Monument to Stephen and Elizabeth Niblett.
c.1766.
It is attributed to Nicholas Read (d. 1787) apprentice of Roubiliac (1746).
Biographical Dictionary... Yale 2009 - refs Gunnis but gives no further info.
If not Read I would suggest perhaps William Tyler (d.1801) also an apprentice of Roubiliac.
It is the first and only memorial of a woman in the chapel - the unusual design is both bold and unique.
To the right of two lamps an academic gown is cast over a pile of books, all superbly sculpted in white marble.
Niblett was elected Warden (head) of All Souls College, Oxford in 1726, a post he held until 1766.
During his time as Warden of All Souls College, he was also Vice-Chancellor of Oxford University from 1735 until 1738
The Nibletts lived in the warden’s lodgings for forty years and died within fifteen months of each other
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Elizabeth Niblett. (d. 1765)
Anonymous portrait.
All Souls College, Oxford.
Inscribed on the back Stephen Niblett S.T.P. Coll. Omn. Anim. Custos Witts pinxit 1744.
https://artuk.org/discover/artworks/mrs-elizabeth-niblett-d-1765-221553