Start by making the pastry. First sieve the flour and a pinch of salt into a large bowl, holding the sieve up high to give the flour a good airing. Then add the butter and lard and, using only your fingertips, lightly rub the fats into the flour, again lifting the mixture up high. When everything is crumbly, sprinkle in 1 tablespoon of water. Start to mix the pastry with a flat-bladed knife and then finish off with your hands, adding a few more drops of water until you have a smooth dough that will leave the bowl clean. Then pop the pastry into a plastic bag and let it rest in the fridge for 30 minutes.Next, transfer the pastry to a flat, lightly floured surface and roll it out to a circle about ½ in (1 cm) larger all round than the rim of the tin. Cut a ½ in (1 cm) strip from the edge of the pastry, dampen the rim of the tin with water and fix the strip round it, pressing down well. Dampen the strip before lining the tin with the pastry circle, making sure you don't trap any air underneath it. Then prick the base all over with a fork. Place the tin on the baking sheet and bake on a high shelf in the pre-heated oven for 20-25 minutes, or until cooked through. After that, remove the pastry case from the oven and immediately lower the heat to gas mark 2, 300°F (150°C) for the meringue.Meanwhile, make the filling. Measure 10 fl oz (275 ml) cold water into a jug, and spoon the cornflour and sugar into a bowl. Add enough of the water to mix the cornflour to a smooth paste, then pour the rest of the water, along with the grated lemon zest, into a small saucepan. Bring this up to the boil, then pour it gradually on to the cornflour, mixing all the time until it is smooth. Now return the mixture to the saucepan and bring it back to the boil still mixing. Next, simmer very gently for about a minute stirring all the time to prevent it from catching. Then remove the pan from the heat and beat in the egg yolks, lemon juice and lastly, the butter. Now pour the lemon mixture into the pastry shell and spread it out evenly.Finally, for the meringue, use a large, spanking clean, grease-fee bowl and in it whisk the egg whites until they form stiff peaks. Now beat in a quarter of the sugar at a time until it is all incorporated, then spoon the meringue on top of the pie, taking it to the very edge of the pastry rim with a palette knife, so that it seals the edge completely (You can also make a few decorative swirls).Bake in the oven on the centre shelf for 45 minutes, by which time the meringue will have turned pale beige, and be crisp on the outside and squashy within. Serve warm or cold, but if warm, leave it to settle for about 20 minutes. Chilled pouring cream is a nice accompaniment.