Dear Friends and Colleagues,
 
Thank you for the suggestions and other comments that you've sent me off list concerning the (continuing to be) elusive Holy John of Bower. I am very grateful.  Several of you have asked if I could supply more context to help with thinking about it, so here is what I know, at the moment, about the reference. I hope that this is appropriate use of the REED-L list.
 
The reference appears in the Grimsby Borough Court Book for 1501-39 (NELA 1/102/2) in an order on 18 June 1527 directing six men of Grimsby "to prepare for the play of holy Iohn of bowre."  Of the six, the man listed first is Peter Mason.  His will (LA: LCC Wills 1535-47/5v-6v) includes this bequest: "Item I bequeth to the gylde of holly Iohn of bower yat I am alderman of / iij s iiij d." He also left lesser amounts to the Trinity, Ascension, Assumption, and St. George guilds of St James Parish Church of Grimsby. He was buried in that same church.  Local historian Edward Gillett says that St. James was "the principal church" of Grimsby and that the Guild of St. John of Bower may have had an altar in the church.  He also says that the guild hall was "often called St. John a bower house" and that it lay "on the south bank of the West Haven' (i.e., near the docks).
 
Stan Kahrl, who included the court book reference in his Malone Society volume, assumed that the entry refers to an unknown saint of that name, and that the Guild of St. John Bower to which Mason refers was perhaps a group within either the Trinity, Ascension, or St. George guilds, to whom Mason had also left money.  Stan's own opinion, he says, is that Mason was alderman of the powerful Mariners' Guild.
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My own inclination is to think that the entry does not refer to an hitherto unknown saint but to a play (of unknown content) belonging to the Guild of St John of Bower. Tht guild seems to have been a guild independent of the others, because Mason lists his bequests to them separately from St John of Bower Guild.  In the same year as the court book entry (1527), the nearby town of Louth paid the players of Grimsby for speaking the banns of their play.  It seems reasonable to assume that the play of the court book and the one mentioned in the Louth records are the same play, and that this play was "the" town play of Grimsby,  just as Donington, Boston, Long Sutton, et al, had a single play representing the entire town and/or parish.  
 
I don't think that the aldermanship to which Mason referred was the Mariners' Guild.  Grimsby had two parishes (St. Mary and St. James).  The Mariners' Guild was associated with St. Mary's church and kept its Noah Ship there, whereas Mason's life was centered in St. James parish church and in the John of Bower Guild. 
 
What else can we know of St. John of Bower Guild?  It must have been a very powerful guild to have been responsible for the town play, and to share a name with the guild hall.  Of the six men named in the order, at least three can be identified as being were among the town's elite sea merchants. 
 
Peter Mason.  In 1523 he was was identified as being one of only two townsmen in Grimsby with a worth assessed as more than 40 pounds.  He was mayor in 1534.  His will mentions houses, lands, tenements, silve, and money.
 
Michael Mason.  His son. A corn merchant.  In 1532 he shipped 40 quarters of corn on the Leonard of Newcastle, and in 1534 was licensed to ship 200 quarters of wheat.
 
Richard Empringham.  From a landowning family; one of Mason senior's executors.
 
Grimsby historian S. H. Rigsby observes that there is no evidence of a gild merchant in Grimsby, but the Guild of St. John of Bower seems to have had some of the qualities of one.  All the important guilds except the Mariners' Guild were associated with St. James Parish, and of them, St John seems to have been the most powerful.  I'm inclined to think that it was the town's most important spiritual guild, that its principal membership was the town's powerful burgesses and merchants, and that the six men appointed were similar to the playmasters recorded in other towns, commissioned not to mount the play but to oversee it.
 
One final thought (perhaps fanciful).  One of the meanings of bower is anchor or anchors.  Grimsby was first and last a sea port built upon the fishing industry.  Its merchants and sailors were its life.  One can imagine the two guilds (Mariners and St John) as being, so to speak, the ship and the anchor of the town.  St. John Baptist has important redemptive associations with water, and the order to prepare the play was given on 18 June, just a week or so before the Feast of St. John Baptist.  Perhaps he is a more likely candidate that John of Beverly as the subject of the play?
 
Thank you for letting me muse aloud. Thank you for your help.
 
Jim