Prepare the pastry base – Put the self-raising flour, vegetable suet, and caster sugar into a bowl. Mix well so the suet is evenly distributed, which helps create a light pastry.

Bring the dough together – Add the cold water gradually, mixing with a spoon until a soft but not sticky dough forms. Stop as soon as it comes together to avoid toughness.

Roll out evenly – Turn the dough onto a lightly floured surface and roll it into a rectangle about 1 cm thick. Aim for even thickness so it cooks uniformly.

Spread the jam – Spoon the jam over the dough, spreading it evenly and leaving a small border around the edges to stop it leaking out during rolling.

Roll into a log – Starting from one long edge, roll the dough up tightly like a Swiss roll. Keep the roll firm but gentle so the layers stay neat.

Wrap securely – Wrap the roll tightly in baking parchment and then in foil or a clean tea towel, twisting the ends to seal. This helps the pudding hold its shape while cooking.

Cook until tender – Steam the roly-poly until the pastry is soft and cooked through, or bake in a covered dish with a little water in the base until tender.

Rest before slicing – Leave the pudding to stand for a few minutes before unwrapping. This allows it to firm slightly and makes slicing easier.