Good Housekeeping Institute all butter mince pies, plus some cheaper Iceland mince pies. Purely for scientific reasons, to allow a quality cross check
Now cross checked, and (“all butter” pedantry aside) I should have bought more of the GHI pies. The Iceland ones are pretty crap – the case isn’t too bad, but the filling is too liquid, and needs a bit more acid to overcome the cloying sweetness.