Add cold water little by little working the dough into a bowl. Knead until you have a smooth dough (you might need to add flour or water).

Wrap the dough into cling film and place in the fridge for 2 hours (or in the freezer for 1/2 hr).

When you are ready to assemble the pie, pre-heat the oven to 200°C/400°F/Gas 6.

Line a pie dish with baking sheet. Roll out 3/4 of the pastry on a surface dusted with flour. Place pastry at the bottom of the pie dish.

In a large bowl, trim and cut the rhubarb in 1 cm chunks. Add the strawberries (hulled and quartered). Add the mashed bananas.

Mix well together with sugar, corn flour and vanilla.

Transfer the fruit mixture to the pie dish and flatten carefully.

To make the lattice, roll out the rest of the dough and cut long thin strips with a knife (or, if you have one, a fluted pastry wheel). Place one layer of strips on top of the pie evenly spaced. Add another layer of strips perpendicular to the first layer.

Dust pie top with 1 Tbsp of brown sugar.

Place in the oven for 20 mins then reduce oven temperature to 180°C/350°F/Gas 4. Cook for around 1 hour until pastry is golden.

Remove from oven and leave to cool completely before serving so that the juices can solidify.