Robert of Bury joined a small group of 12th-century English unofficial saints of strikingly similar characteristics: all young boys, all mysteriously found dead and all hailed as martyrs to alleged anti-Christian practices among Jews.

Jocelyn de Brakelond, a monk of Bury St. Edmunds, later wrote a chronicle covering this period.

John Lydgate wrote a poem entitled Prayer for St. Robert, which implies that the story of his death closely mirrored that of William of Norwich, in which Jews are supposed to have kidnapped the child with the help of a Judas-like Christian accomplice, and tortured and then crucified him over Easter in a parody of Jesus's death.

An illustration to a Latin prayer to Robert depicts him lying dead in a ditch beside a tree, with an archer nearby shooting an arrow upwards, illuminated by a giant sun.

"[5] Bale, referring to the research of Hillaby, suggests that the cult was promoted at a time when the abbey at Norwich was attempting to assert authority over Bury.

He argues that Samson of Tottington, Abbot of Bury from 1182 to 1211, decided that the town needed the cult to preserve its independence.

[6] The cult of Robert may have served as a contributing factor in the later violent attack upon the Jews of Bury St Edmunds on Palm Sunday 1190, in which fifty-seven were killed.