In a bowl mix together lemon juice, mint leaves, peppercorns and red chilli flakes.
Divide this marinade into two equal parts and marinate watermelon cubes and cheese cubes separately in the refrigerator for one hour.
Take a toothpick and skewer a cube of watermelon followed by a cheese cube and another watermelon cube. Repeat this for rest of watermelon and cheese cubes. Serve chilled.