Combine the blackberries, raspberries, blueberries, raspberry jam and sugar in a medium saucepan. Bring to a simmer and cook for 1 minute. Stir in the lemon juice and put aside to cool.
Line a 5-cup soufflé dish or mixing bowl with plastic wrap, leaving a 13cm overhang all round. Slice the bread in half on the diagonal and arrange the triangular slices on the bottom and sides of the dish (there will be bread left over for the top).
Spoon the berries and juices into the bowl. Cover with the remaining bread, trimming all sides. Cover with plastic wrap and fold the overhang over the top. Weight down with a heavy can. Refrigerate for at least 8 hours. Unmould onto a serving plate and remove the plastic. Cut the pudding into wedges and serve with the whipped cream.
I have made this pudding over the years using fresh fruit and instead of using jam, I add a red jelly, made with only 1 cup water. I do not then need to press the fruit down. Just as tasty!! - 26 Dec 2009