Preheat the oven to 160°C/325°F/ Gas 3. Grease and line an 18 x 28 cm (7 x 11 in) cake tin.

Stir together the flour, bicarbonate of soda and ginger, then stir in the oatmeal. Mix the sugar, margarine and golden syrup in a saucepan, then stir into the flour mixture. Beat in the egg and mashed bananas.

Spoon into the tin and bake for about 1 hour, or until firm to the touch. Allow to cool in the tin, then turn out and cut into squares.

Sift the icing sugar into a bowl and stir in just enough water to make a smooth, runny icing. Drizzle the icing over each square and top with a piece of stem ginger.