Method

• 1.
  Cut 12 pieces of watermelon to the size of ice cubes, place on a baking tray lined with baking paper and freeze overnight.
• 2.
  The next day, heat a chargrill pan or barbecue over high heat. Cut the remaining watermelon flesh into wedges and cook for 2-3 minutes each side until charred.
• 3.
  Remove from the pan and cool completely. Place in a food processor with the sugar and whiz until smooth.

• 4.
  Strain through a fine sieve, discarding excess pulp. Chill until completely cold.
• 5.
  To serve, divide watermelon ice cubes among four serving glasses, then divide gin, tonic water, mint leaves, watermelon juice and lemon slices among glasses and stir to combine. Serve immediately.