Grease a 1.5 litre heatproof basin.
Mix the flour and suet in a bowl, then add the milk and 100ml of water to form a soft but firm dough.
Roll the dough into a large circle on a floured surface and cut out one quarter to use for the lid.
Line the basin with the larger pastry piece, pressing the cut sides together to seal.
Place half the butter and half the sugar into the bottom of the lined basin.
Prick lemons thoroughly with a skewer and place them in the bowl, then cover with the remaining butter and sugar.
Roll out the reserved pastry quarter into a round, place it on top, and seal the edges.
Cover the basin with pleated aluminium foil and secure tightly with string, creating a handle.
Lower the basin into a large pan of boiling water so the water reaches halfway up the sides.
Cover and simmer for 3 to 4 hours, topping up the water as necessary.
Turn the pudding out into a deep dish and serve immediately with cream and ice cream.