Combine the 120g of light brown sugar and 360ml of water in a medium saucepan over low heat. Stir until the sugar completely dissolves and the liquid is clear and warm. Add the 150g of lightly mashed raspberries, 150g of sliced and lightly mashed strawberries, and 150g of lightly mashed blueberries simultaneously. Add the 2 pinches of fine sea salt. Keep the heat specifically at the lowest possible setting — warm rather than simmering. Stir gently to distribute the berries through the warm liquid and encourage colour and aromatic release. Warm for 2–3 minutes only. The 2–3 minute window is the most precisely limited berry heat application in the entire crowd collection. At this brief exposure the specific extraction sequence across the three berry types is: Raspberry: the vivid anthocyanin pigments from raspberry's surface cells and the volatile ester aromatic compounds responsible for fresh raspberry's bright, vivid, slightly tart freshness both release rapidly in the first 2 minutes of warm liquid contact. Beyond 3 minutes the jam-adjacent cooked-raspberry character begins developing. Strawberry: the surface furanone compounds responsible for fresh strawberry's characteristic warmth release within 2–3 minutes at this temperature. Beyond this the cooked-strawberry note specifically develops and the fresh-fruit register diminishes. Blueberry: the anthocyanin pigments release readily within the first minute of warm liquid contact; the deeper berry aromatic compounds require the full 2–3 minutes. Blueberry's deeper character is the most tolerant of the three to brief heat but still shifts toward cooked character at extended temperatures. Remove from the heat at the 2–3 minute point. Add the lemon zest immediately. Cover and steep for 5–8 minutes — the off-heat zest infusion occurring as the combined berry-syrup mixture cools gradually, providing the integrated lemon aromatic bridge without additional heat exposure to the berry compounds. Strain through a fine-mesh sieve, pressing gently but firmly on the mixed berry solids. The combined berry pulp will be a mix of raspberry seed-containing mass, blueberry skin fragments, and strawberry fibrous pulp — press firmly enough to extract the maximum vivid syrup without forcing the seed fraction or the driest pulp through. Raspberry seeds are the specific concern; press until the seeds begin to feel resistant rather than until the solids are completely dry. Allow to cool completely. The cooled syrup should be a vivid, specific berry-red-to-purple — the combined anthocyanin pigments from raspberry and blueberry alongside strawberry's lighter red producing a vivid, complex, dark berry colour.

Pour the cooled mixed berry citrus syrup into the large pitcher. Add 2.2 litres of ice-cold water and, if using, 60ml of fresh lemon juice. Stir gently until fully combined. The lemon juice's function in this preparation is optional but recommended for the specific reason stated: without it, the combined berry syrup at crowd dilution produces a specifically pleasant but specifically soft, specifically berry-water-adjacent result. The combined sweetness of three berries with the light brown sugar in 2.2+ litres of water is sufficient for pleasantness but lacks the acid dimension that makes the preparation specifically bright and specifically refreshing. At 60ml in 2.6+ litres the lemon juice is below any threshold of detectable lemon flavour — it functions purely as an acid sharpener that makes the berry characters more specifically vivid. Taste: the drink should be immediately and specifically of three berries simultaneously — a warm, complex, vivid berry character where raspberry's brightness, strawberry's warmth, and blueberry's depth are all perceptible without any individual one specifically dominating. The light brown sugar's warm caramel-adjacent note specifically bridges the three different berry aromatic profiles into a more unified, more specifically cohesive berry character than white sugar's neutral sweetness would provide. Add more lemon juice up to 90ml if the berry character needs sharpening. Add more cold water up to 2.8 litres if the concentration is too intense.

Cover and refrigerate for 1–2 hours. Stir once before the first pour. Distribute fresh berries and lemon slices across the garnish arrangement for visual impact. Serve cold.