Grapefruit and Ginger Meringue Pie

Name: Grapefruit and Ginger Meringue Pie
Ingredients: 250g (9 oz) plain flour, plus extra for dusting; 65g (2⅓ oz) icing sugar; ½ tsp salt; 3 tsp ground ginger; ½ tsp ground cinnamon; 125g (4½ oz) butter, chilled and cubed; 2 large free-range egg yolks; 1 small free-range egg, beaten; 2 pink grapefruit, juice and zest only; 3 white grapefruit, juice and zest; 1 red grapefruit, juice and zest; 70g (2½ oz) fresh root ginger, peeled and sliced; 5 large free-range egg yolks; 3 large free-range eggs; 60g (2¼ oz) caster sugar; 2 tbsp cornflour; pinch salt; 70g (2½ oz) unsalted butter, cubed; 300g (10½ oz) caster sugar; 2 tsp lemon juice; 140g (5 oz) egg whites, at room temperature