Preheat the oven to 200°C.
Mix the flour, suet, and salt in a large bowl.
Add enough water to form a soft, non-sticky dough.
Knead the dough briefly on a floured surface.
Roll the dough into a 20cm square with a 1cm thickness.
Spread a thick layer of jam over the dough leaving a 1cm border.
Dampen the border with water and roll up the dough loosely.
Pinch the ends to seal and place on buttered silicone parchment.
Pleat the paper to allow for expansion and twist the ends.
Place the roll in a tin and set over a roasting tin filled with boiling water.
Bake on the top rack for 35 to 40 minutes.
Slice thickly and serve with homemade custard.