familysearch has images of parish registers for St John, Newcastle. They are browse only, and as far as I can see there are only baptisms and burials. In 1838 names of officiating ministers are Maughan, Simpson, Wright ..and R N L Jones, who always signs with initials for his forenames.
There was a C of E minister named Pryce Jones at this time, who was vicar of Helmdon in Northamptonshire. It is possible that he was a relative of R N L Jones, who happened to be visiting and assisting at St John's for some reason when the marriage took place. P. Jones/Pryce Jones was performing baptisms and burials at St John's in September and October of 1838.