Begin by removing the bowl from your slow cooker and lightly greasing with vegetable oil. Cut out a circle of baking paper to fit in the bottom of your slow cooker bowl and lay in the bottom of the bowl. Lightly grease the paper and then pour the golden syrup on top. Sprinkle the breadcrumbs on top and set aside.
Cream together the margarine and sugars until pale and light then gradually add the eggs. Fold the flour into the mixture followed by the milk, the vanilla
extract and the lemon zest.
Spoon the batter on top of the golden syrup and breadcrumbs in the slow cooker bowl and smooth out the top.
Place the bowl back into the slow cooker and close the lid. Cook for 2 hours on high or until a skewer comes out clean.
Invert the cake onto a serving plate and serve with lashings of clotted cream!