The church famously possesses the head of Archbishop Simon Sudbury, who was beheaded by rebels during the Peasants' Revolt in 1381.

[4] Archbishop Sudbury was beheaded by rebels during the Peasants' Revolt in 1381 because of his involvement with the poll tax; his mummified head was brought to the church,[5] and is kept in a niche in the vestry wall.

[6] In March 2011 a CT scan of Sudbury's head was performed at the West Suffolk Hospital to make a facial reconstruction, which was completed in September 2011 by forensics expert Adrienne Barker at the University of Dundee.

The college building was situated on 3 acres (1.2 ha) of land adjacent to St Gregory's churchyard, believed to have been the site of the house of Nigel Theobald, the father of Simon and John.

After passing through numerous hands, it was eventually purchased by the Borough of Sudbury for use as a workhouse and the remaining medieval fabric was demolished in 1836 to make way for a more suitable building.

[14] Only the heavily restored gateway survives, standing on the west side of the churchyard; it is a Grade II listed building.

[3] The lowest section of the 12-foot (3.7 m) tall cover was adapted in the 19th century to telescope upwards, so as to avoid having to lift the whole edifice in order to use the font.

[18] A chest tomb for Thomas Carter, who died in 1706, has a Latin inscription that reads: "Traveller, I will relate a wondrous thing.

On the day which the aforesaid Thomas Carter breathed his last, a Sudbury camel passed through the eye of a needle, if thou hast wealth, go do likewise.