If the pastry base is uncooked, cook it following the instructions here.

Collect together your equipment (see Recipe Notes below) and ingredients.

Measure the cold water into a jug and spoon the cornflour and sugar into a bowl. Add enough of the measured water to mix the cornflour to a smooth paste.

Pour the rest of the water along with the lemon rind into a small saucepan. Bring this up to the boil then pour it onto the cornflour paste and mix until smooth.

Transfer the mixture back to the saucepan and bring back to the boil stirring all the time. Continue to stir and simmer for 1 minute.

Remove the pan from the heat and beat in the butter and lemon juice.

Now add the egg yolks and thoroughly stir.

Pour the lemon mixture into the pastry shell and spread it out evenly. If you have time let the mixture cool and set a little before topping with the meringue mixture – it will be a lot easier!

Preheat the oven to Fan Oven 130°C/150°C/300°F/Gas 2

Whisk the egg whites in a large bowl until they form stiff peaks.

Beat in a quarter of the caster sugar at a time until it is all incorporated.

Spread the meringue mixture all over the filling to the very edge of the pastry rim so that it seals the top completely. Make some decorative swirls with your knife.

Cook in the oven for 45 minutes by which time the meringue will have turned pale beige and crisp on the outside and will still be soft and fluffy on the inside.

Serve warm or at room temperature either as is or with some fresh cream.