I've discovered some home made mince pies (frozen after production, un-cooked) which were made by following Delia's Traditional Mince Pie recipe this time last year (lard & butter based pastry and shop bought mincemeat). They've lived in the freezer at -20°C in an airtight container since production.
Will they have suffered any quality degradation / no longer be safe to eat?
They will certainly be safe assuming your freezer has operated properly throughout the last year.
Some quality degradation is possible, especially freezer burn on the outside if they were not wrapped extremely well. A buildup of visible frost inside the wrapping is a sign this is extremely likely, although it can happen even without the buildup.
Rancidity of the butter in the pie crust is also possible, but not terribly likely.
Still, since you have the pies, there is no harm in baking one and seeing how they turned out.
