Heat the oven to Gas 3, 170°C, fan 150°C. Grease a 900(2lb) loaf tin with nonstick baking paper.
Place all the cake ingredients in a mixing bowl and beat well with a wooden spoon. Pour into the tin and bake for 1 hour and 15 minutes, or until golden, firm to the touch and a skewer comes out clean. Allow to cool in the tin for 10 minutes, then turn out and cool on a wire rack. Remove the paper and leave to go cold.
Warm the marmalade for 30 seconds in a small pan and brush over the cake. Roll the marzipan out on to a work surface dusted with icing sugar, into a rectangle large enough to cover the top and side of the cake. Drape over the cake and smooth down well. Trim off any excess.
To serve, dust with icing sugar and for a special occasion, decorate with fresh primroses or violets (don't eat the flowers).
Will keep (without the flowers) for up to a week in a cake tin, or can be frozen without the marzipan for 3 months.
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