Ingredients: 
10 elderflower heads  
600 mls water 
900 g sugar 
1 lemon thinly sliced 
45 g citric acid 
  
Steps: 
Pick the elderflowers when they are dry and shake off any insects (insects do like elderflowers!).  Bring water to boil, add the sugar and stir to dissolve. Remove from heat and leave to cool for 10 minutes.  Add the elderflowers and stir. Then add the thinly sliced lemons and citric acid.  Cover and leave overnight. 
  
Next day, pour the syrup through a sieve and then pour into glass bottles and store in the fridge or a cool place. I have found that the syrup lasts a long time in the fridge (if you can hide it from the family) but it really needs to be frozen for longer storage.