Preheat the oven to 220C/200C Fan/Gas 7.
To make the meringue, line a 35x30cm/13x11in Swiss roll tin with baking paper, allowing 2cm/½in to hang over the sides of the tin.
Whisk the egg whites in a clean, glass bowl to soft peaks. Gradually add the sugar, whisking constantly, until the mixture becomes thick and glossy. Add the vanilla extract, vinegar and cornflour and whisk until combined.
Transfer the meringue mixture to the lined tin and spread out evenly. Put in the oven and immediately lower the temperature to 180C/160C Fan/Gas 4.
Bake for 35 minutes, or until pale beige and crusty on top. Set aside to cool completely.
To make the filling, whisk the cream to soft peaks. Add the vanilla extract and icing sugar and whisk to combine.
With a clean tea towel placed over the top of the meringue, turn out onto a work surface. Lift the tin and peel off the baking paper.
Spread two-thirds of the whipped cream over the meringue. Cover with 500g/1lb 2oz of the peaches and 200g/7oz of the blackberries and sprinkle over 50g//1¾oz of the the almonds.
To roll up the pavlova, start with longest side closest to you. Using the tea towel, roll the meringue up and over so the edges come together to form a log (it won’t roll as much as a roulade). Pull away the tea towel as you roll and slide onto a platter with the seam facing downwards.
To serve, pipe or spoon the remaining cream down the length of the roulade and top with the remaining peaches, blackberries and almonds.