Preheat the oven to 180°C / 350°F / Gas mark 4.
Grease a 900g loaf tin and line the base and ends with a long strip of baking parchment.
In a large bowl mix the butter, sugar, flour, eggs and vanilla extract until pale and creamy – the mixture will be very thick. About 5 minutes.
Spread one-third of the cake mix into the tin, then scatter over 50g of the fruit.
Carefully dot and spread another third of the cake mix on top, and scatter with another 50g fruit.
Finally dot the rest of the cake mix over and gently spread with the back of a spoon.
Bake for 1 hour, until an inserted skewer comes out clean.
Poke the cake all over with a skewer. In a bowl, add the remaining 75g of fruit with the granulated sugar.
Stir in 1 tablespoon of the citrus juice mashing a little of the fruit as you go. If it’s a bit dry, add a bit more juice and spoon over the cake.
Leave in the tin until the cake is cool.