The “fourth man” in the Italian Boy case was Michael Shields, a gravedigger turned carrier for bodysnatchers. Though released without charge, Shields was well known in the bodysnatching community as a strong, reliable and discreet porter: he ferried corpses around London in a large straw basket placed upon his “porter’s knot” on top of his head.
He had previously worked as a careaker for St Mary Moorfields Roman Catholic chapel, but was dismissed for stealing church silverware. St Mary Moorfields is pictured below in 1827, in its Finsbury Circus incarnation. It had opened in 1820 and stood on the north-east corner with Blomfield/Bloomfield Street. Next, Shields went on to be a fruit, veg and flower porter at Covent Garden market, as well as a gravedigger at St Giles-in-the-Fields; from there, it was a sideways step into transporting around town the bodies dug up by resurrection men.
Below is a contemporary sketch that did the rounds during the Italian Boy trial, showing Shields turning up at King’s College in the Strand on 5 November 1831 with John Bishop, Thomas Head and James May; he was delivering the corpse that would lead to the four men being arrested. Shields was released from Bow Street magistrates’ court as there was little interest in pursuing this lesser charge when it appeared that the Italian Boy case was in fact a major multiple murder inquiry.
St Mary Moorfields was demolished in 1899 (when the interior, below, was sketched) and moved to new premises in nearby Eldon Street, where it still thrives.
You can read more about the present-day church here https://parish.rcdow.org.uk/moorfields/about-the-parish/