The Tyrells of Thornton were mostly interred in the family vault under the chancel or chantry chapel; Sir Toby in 1671 referred in his will to being buried 'in the chauncel at Thornton as neare to my deare father as may be', and his son, Timothy, made a similar request in 1674. Frances, the wife of Harry of Whaddon Chase was 'Buried in Barton's Isle' in 1668, and Harry himself, in 1704, 'was buried in this Church in ye place by ye Chanucell called Barton's Isle above ye vault'. When the chancel and chantry were demolished by Thomas Sheppard he built a new vault on the north side of the church (covered by the newly-constructed north aisle in 1850) in which is set a stone bearing the inscription 'This vault was built by order of Thomas Sheppard, 1784'. The entrance to this vault is by steep steps under the north side of the east end of the church, the opening being covered by a heavy slab and obscured by several inches of earth. The Tyrrells were all moved into this new vault, the complete coffins being stacked up on top of each other at the far end with next to them a small brick retaining wall behind which were placed the other remains. In 1965 this was a mound of mouldering wood, metal coffin furniture and bones. The remainder of the vault is taken up by the coffins of the Sheppard family.

SEE PLAN OF VAULTS

It is said by local Tyrrell descendants that the memorials in the church to the Tyrells were torn down and thrown into the river when the building was altered by Thomas Sheppard. Although other monuments in the church undoubtedly were destroyed at this time, there evidently were none concerning the lords of Thornton, as is clearly demonstrated by the detailed account of the church in 1735, that is before it was 'modernised', given by Browne Willis, who wrote: 'not the least memorial for any one...' of the Tyrrell family interred in the vault; 'vix.: no less than 6 baronets, and some of their Ladies and Children, of above 30 of whose Interments we have an account of from George Tyrrill's time, Anno 1570'.

Theodosia, the daughter of Sir Edward Tyrrell of Thornton, married Edmund West of Marsworth, probably in 1607; his first wife died in 1606 and Theodosia's first child was baptised in March 1608. An elaborate altar tomb at Marsworth, the work of Epiphanius Evesham, bears among other carvings that of the arms of West impaling Tyrrell.

The earliest monument to a member of the West family in this church is the floor slab to Nicholas, who obtained the title to Marsworth in 1565, and who died in 1586. Much of the brass inlay of his memorial stone is missing, but the remains include a shield of arms of West impaling about ten quartered coats. This is worn and difficult to decipher, but one of these quarterings appears to be Tyrrell. If this is so, it would argue for an earlier connection between the families of Tyrrell and West, though the Tyrrell quartering could conceivably have been brought in by some other family with whom the Wests had intermarried.