Place the egg whites in a large clean bowl and beat with an electric whisk until frothy. Add the lemon juice and continue to beat whilst gradually adding all the sugar until stiff peaks form. Take heaped tablespoons of meringue and dollop them onto the lined baking tray, spreadign them out slightly with the back of the spoon. Place into the oven to 70 minutes then switch the oven off and leave in the oven with the door closed for a further hour.