Blitz the lemons in a food processor or blender with half of the sugar, some ice cubes and 500ml/18fl oz water. Strain the juice into a jug and reserve.
Tip the lemon pulp back into the food processor. Add the rest of the sugar, more ice cubes and 500ml/18fl oz water and blitz again. Strain this into the jug with the reserved juice (discard the pulp). Serve with lots of ice.
Give it a twist
For a sweeter taste use oranges instead of lemons, or add some lime juice for extra zing.
To take to the picnic
Pour the lemonade in a flask or drink bottle.