Rinse the mint and reserve 12 leaves for later.
Place in a saucepan with 150ml of cold water. Place over a high heat and bring to the boil. Reduce the heat and simmer for 5 minutes to allow the mint flavour to infuse.
Strain into a large measuring jug and sprinkle over the powdered gelatine. Whisk until the gelatine has dissolved.
Dissolve the sweetener in the lime juice, then add to the gelatine along with the white rum. Whisk well.
Top up with diet lemonade, until you have 570ml (1 pint).
Divide the strawberries between 4 glasses, and place 2 mint leaves in each.
Pour the jelly mix evenly into 4 glasses.
Cover and refrigerate for at least 8 hours, until the jelly has set.
Decorate with a mint leaf before serving and enjoy.