Hey, have you considered that the mysterious fruit might have been quince? It has that tartness and sweetness balance you mentioned. The fruit was pretty popular back in the day for pies and jams. You might want to look into old quince custard pie recipes!

As someone who takes their pies *very* seriously, I'd argue that while some stadium pies are passable at best, there are a few grounds out there hiding genuine culinary surprises. If you ever find yourself at Bramall Lane, the steak and ale there is an unsung hero among match-day meals. …