Prepare the watermelon purée: Place the chopped watermelon in a blender and blitz on high for 45 seconds, until the mixture is completely smooth and a vibrant, opaque pink. You should see no solid flecks remaining. The purée should smell intensely sweet and floral.

Strain the purée: Pour the purée through a fine-mesh sieve set over a large bowl. Use the back of a spoon to press the liquid through, leaving behind a pale, dry pulp. You should yield about 350ml of clear, ruby-red juice. Discard the pulp.

Make the syrup base: In a small jug, whisk together the strained watermelon juice, lemon juice, and honey until the honey has fully dissolved. The mixture will turn a slightly lighter coral shade. Taste it — it should be sweet with a sharp, tangy finish. Cover and refrigerate for at least 1 hour until thoroughly chilled.

Prepare the glass rims (optional but impressive): Run a lemon wedge around the rim of each glass. On a small plate, mix a pinch of sea salt flakes with the caster sugar. Dip the rim of each glass into the mixture, twisting gently to coat evenly. Tap off any excess.

Assemble the first layer: Fill each glass halfway with ice cubes. Pour 100ml of the chilled watermelon syrup over the ice. The syrup should settle at the bottom, creating a dense, deep pink layer.

Add the sparkling element: Slowly pour 125ml of sparkling water down the side of each glass, tilting the glass as you pour. This gentle technique preserves the carbonation and creates a distinct, graduated colour from dark pink at the base to pale, fizzy pink at the top. You should hear a satisfying hiss as the bubbles rise.

Garnish for impact: Gently stir the drink once with a long spoon to marry the layers slightly. Garnish each glass with a sprig of mint and a thin wheel of lemon. The mint should sit on the surface, releasing its aroma as guests bring the glass to their lips.