Arms: Gules, a saltire Argent.
Plain English: A red shield bearing a silver or white diagonal cross.
The family
The Nevilles were among the most powerful noble families of fifteenth-century England. Their principal estates lay in northern England, but marriage, inheritance and royal service gave them influence throughout the country.
The Salisbury branch descended from Richard Neville (c.1400–1460), who married Alice Montagu, daughter and heiress of Thomas Montagu, Earl of Salisbury. Through this marriage Richard became Earl of Salisbury. Their children included Richard Neville, Earl of Warwick (1428–1471), the famous “Kingmaker”, one of the dominant figures in the Wars of the Roses.
The arms
The basic Neville arms were Gules, a saltire Argent — a white diagonal cross on a red field. It is one of the simplest and most readily recognisable coats represented on the St Thomas’s ceiling.
As the Nevilles acquired estates and titles through marriage and inheritance, these arms were frequently combined with other family coats in more elaborate quartered shields.
Salisbury and Wiltshire
The Neville connection with Salisbury came principally through Alice Montagu and the earldom of Salisbury. Her father Thomas Montagu died in 1428, and Alice inherited his estates and title. Her husband Richard Neville was subsequently recognised as Earl of Salisbury in her right.
The Neville arms therefore represent a family closely connected with the Salisbury title during the period in which the St Thomas’s ceiling was being created.
On the St Thomas’s ceiling
The Neville arms appear at:
The surviving shield clearly shows the distinctive white saltire on a red field.
Both RCHME and Buckeridge identify the arms as Neville.
Sources
RCHME and Buckeridge — identification of the St Thomas’s ceiling heraldry.
Standard heraldic and genealogical accounts of the Neville Earls of Salisbury.