Watermelon & grape cooler

Put the prepared fruit, mint leaves, lime juice, 250ml ice-cold water and 2 tbsp maple syrup or honey in a high-speed blender. Whizz until the mixture is as smooth as possible then taste for sweetness, adding a further 1 tbsp maple syrup or honey if needed (this will depend on how sweet the watermelon and grapes are). Blend again to combine then pour the mixture into a sieve set over a large jug or bowl (at least 1.2 litre capacity), scraping with a spatula or spoon until all the liquid has passed through. This will remove any grape skins left in the mixture.

Transfer to a flask to keep the liquid cool. Fill a second flask with ice cubes to keep them frozen and, when ready to serve, half-fill 8 glasses with ice, mint sprigs and lime slices. Pour over the watermelon-grape mixture and enjoy.