Pre-heat the oven to 160°C fan. Grease and line the base and sides of a 16 - 18 cm round cake tin, 15 cm square tin, or a large loaf tin with baking paper. Wrap brown paper or newspaper around the outside, and secure with string (this prevents it from being too dry).
Cream the butter and sugar until light and fluffy.
Sift the flours together into a separate bowl.
Beat the eggs into the creamed mixture, one at a time, following each with a tablespoon of the sifted flours (to stop the mixture from curdling).
Sift in the remaining flour and fold in gently with a large metal spoon.
Spoon into the prepared tin. If you want to avoid / minimise a domed top (e.g. if decorating with fondant), scoop 3/4 thickness of the middle section of the cake towards the sides, so that it is a bit like a doughnut. It will even out while baking.
Bake for about an hour and 15 minutes (may be 5 minutes or so either side, depending on your oven, and the tin used) until the cake is golden, firm to touch and a skewer inserted into the centre comes out clean. Leave in the tin for at least an hour, then turn out onto a wire rack to cool completely.
If not serving or decorating until the following day (or two), leave the baking paper on the cake, wrap well in foil and keep in a tin. For tips on how to cover with fondant, see my recipe for 'Flower cake'.