Wash and de-stalk all the fruit and put it into a medium-sized pan.
Add the sugar, 250ml/9fl oz water and lemon juice to the pan.
Bring all of the ingredients to the boil and simmer for 20 minutes.
Tie a jelly bag or a clean sheet of muslin to something appropriate so it can dangle over a bowl. Pour the ingredients into the jelly bag (or muslin) and leave to drip. Do not squeeze the bag to prevent the cordial going cloudy.
Once all the liquid has dripped through (about an hour), pour the syrup into a sterilised jar.
Store this cordial in the fridge and drink within a week.