Mix the flour and suet together in a bowl.
Combine the milk and water in a separate jug.
Gradually stir the liquid into the flour mixture to form a soft, rollable dough.
Roll the dough into a large circle on a floured surface and cut out one quarter for the lid.
Line a greased 1.5 litre basin with the large piece of pastry, pressing the seams to seal.
Place half of the butter cubes and half of the sugar into the bottom of the basin.
Prick the lemons all over with a skewer and place them on top of the sugar and butter.
Fill the rest of the bowl with the remaining butter and sugar.
Roll the reserved dough quarter into a circle and press onto the top to seal the pudding.
Cover the basin with pleated foil and secure tightly with string, creating a handle.
Lower the basin into a large pan of boiling water so it reaches halfway up the sides.
Cover and simmer for 3 to 4 hours, replenishing water as needed.
Invert the pudding onto a deep dish and serve immediately.