Heat oven to 180º C

Butter and line the bottom of a 9 x 20 x 13 cm loaf tin.

In a large bowl, rub the flour, butter and sugar together with your fingers to make fine crumb.

Measure out 5 level tbsp of this mixture into a small bowl for the topping, and mix into the cinnamon and castor sugar. Set aside.

Coarsely grate the apple down to the core and mix in with the eggs and the zest.

Stir the baking powder into the rubbed-in mixture in the large bowl, and then quickly and lightly stir in the egg mixture until it drops lightly from the spoon. Don’t over mix.

Gently fold in 3 quarters of the berries with the metal spoon trying not to break them up.

Spoon into the tin and level.

Scatter the rest of the berries on top. Sprinkle over the topping and bake for 75-80 minutes. Check after 50 minutes and cover loosely with foil if it is browning too much. When done, the cake will feel firm, but test with a skewer to make sure.

Leave in the tin for 30 minutes before turning out, and then cool completely on a wire rack.

Peel off the paper before cutting. Will keep wrap in foil or in a tin for upto 2 days.