To make your own strawberry purée. Remove the stalks from 12-13 ripe strawberries and blend until liquid.
Push the purée through a sieve to remove any seeds and to keep the liquid smooth.
In a large jug, add some ice and squeeze in a whole lemon, ensuring no seeds have landed in the juice. Now add the juices leaving the purée until last.
Stir well with a wooden spoon and add a garnish of lemon slices. Stir in a tumbler.