1Brush a 1.5-litre pudding basin with oil â€“ if you donot have a 1.5-litre pudding basin, use a smaller one and serve any fruit that wonâ€™t fit on the side. Line the basin with a double layer of cling film, overhanging the basin at the top.
2Put the blackberries, cherries, grapes and sugar in a saucepan with 3 tbsp water. Cover and gently heat, stirring occasionally, until the sugar has melted and the fruit is syrupy. Add the currants and blueberries, cover and cook gently for 2 mins more until the fruit is just softened. Take off the heat and cool.
3Strain the fruit into a colander set over a bowl. Leave for 5 mins to drain well, then stir the cassis or Ribena into the captured juices. Trim the crusts from the bread slices and discard, losing as little bread as possible. Then use a pastry brush to spread a little of the berry juices over one side of each slice. Cut a circle from 1 slice (or 2 semi-circles from 2 slices) that will neatly cover the base of the basin, and push in â€“ juice-side down.
4Reserve some bread so that you have enough to cover the top of the basin, then halve the remaining slices into fat fingers â€“ trimming to the correct length to line the sides of the basin. Then, juice-side down, work round the basin, overlapping the edges of the bread slightly and pressing them to stay in place, until the basin is completely lined with bread. Patch any gaps with scraps.
5Reserve a couple of spoonfuls of fruit to serve, then spoon the remainder into the bread-lined basin, squishing the fruit down to level it. Reserve 150ml of the juices with the reserved berries, then pour the rest into the basin, concentrating on pouring it around the edges to soak into the bread. Jigsaw the reserved bread to neatly cover the top and seal in the fruit, this time placing it juice-side up. Loosely cover the top of the basin with cling film. Find a small plate that will fit snugly inside the basin so it is in contact with the pudding and add 4 x 400g cans to weigh it down. Chill overnight with the reserved juice and berries.
6To serve, unwrap and invert the basin onto a serving plate with a lip to hold any juices. Lift off the basin, holding the cling film down tightly as you pull to help you remove it. Peel off the cling film round the pudding. If youâ€™ve any white bread patches visible, spoon over some juice to colour it. Spoon the rest of the berries and juice onto the top of the pud and serve with clotted or single cream, if you like.