Rinse the blackberries and place in a saucepan with the water and sugar.
Bring to the boil and add the lavender. Use a potato masher to crush the fruit slightly.
Leave to cool then strain into a clean jar. This will keep in the fridge for a week and you can use it to drizzle over desserts as well.
Fill a tall glass with ice. Pour in the gin, lemon juice or Limoncello and top up with chilled tonic water.
Add the blackberry simple syrup – it will settle to the bottom of your glass and turn your drink the most beautiful shade of pink.
Add a lavender sprig or a straw and stir before drinking.