Prep time: 15 minutes. Chill time: 2 hours.

Zest the limes into a medium saucepan, add the sugar and 80ml of the water, then place over a low heat for 5 minutes, stirring occasionally, until the sugar has dissolved. Set aside to cool.

Use the palm of your hand to squash and roll the whole limes against a work surface a few times – it’ll help release the juice. Halve and juice them into a bowl or large jug – you need 120ml for this recipe, so juice another lime if needed, or save the spare lime juice for another dish if you have a bit more.

Mix 120ml of the cooled sugar syrup with the 120ml lime juice and add in the remaining 120ml cold water and a pinch of sea salt. Stir well, then taste – it should taste strong, sweet and sour all at the same time, so add in fractions more sugar syrup, water and lime juice to taste. But bear in mind you’re going to chill it in the fridge, so the stronger it tastes now the better, as the cold will slightly mute the flavours.

Strain through a sieve into a clean jug, and chill for 2 hours, or until needed. Serve over ice, with mint sprigs and lime slices to garnish if you wish.