Mix together the flour and suet with a pinch of salt and enough cold water to make a firm dough. Roll out the dough, and use two-thirds to line a two-pint pudding basin. Press the sausage meat into the pastry all round the basin. Chop the bacon and onion and mix together with the sage and sugar. Put this mixture into the centre of the pudding and cover with the remaining pastry. Cover with greaseproof paper and a piece of foil or a pudding cloth. Steam for four hours, and serve with a hot tomato sauce.