1.4 litres boiling water
First scrub the lemons in warm water, grate the zest of 3 of the lemons.
Put the zest in a large bowl and add the squeezed juice of all the lemons (don’t bother to strain the juice at this stage) and the sugar.
Pour in 1.4 litres of boiling water, stir well, cover and leave overnight in a cool place.
Next day stir again and taste to check the sweetness, adding a little more sugar if it needs it.
Now strain through a fairly coarse sieve, as it’s nice if some of the lemon remains. Pour it into bottles, and chill thoroughly.
Serve the lemonade either straight or diluted with water and lots of ice.