Fresh blackberry & lemon sponge

I love this cake; it’s one to make when the blackberries are out in force (be quick with your basket, as it’s not the blackbirds that are cause for concern but nimble-fingered little old ladies). I never skimp on the filling; so often it seems just a mean smear for so much sponge. You may look askance at my use of marge, but it makes for a fluffier sponge.

This is a big cake, Cakezilla, but it should just about fit inside an old biscuit or sweetie tin - a storage method that makes m