Separate the celery stalks and wash well. Trim the root ends and roughly chop, keeping one of the tender, young stems whole to serve.

Put the chopped celery, apple, half the lemon juice and ginger in a food processor or blender and pulse to finely chop. With the motor running, add 50-100ml cold water and blend until smooth.

Strain the juice through a fine mesh sieve into a jug, pressing down with the back of a spoon to extract all the juice. Cover and chill or serve straight away. Stir the juice well, add a squeeze more lemon if you like, and serve in glasses with a piece of the reserved celery stalk.