2. Strain the mixture overnight. In the morning, discard the berries and measure the liquid. Weigh out the sugar - you'll need 455g of sugar to every 565ml of juice.Heat the elderberry juice, lemon juice and sugar in a pan. If you have a sugar thermometer, clip it to the pan. 

3. Heat gently, stirring occasionally until the sugar is dissolved then bring to the boil. Boil vigorously, stirring regularly until setting point (106 degrees) is reached.

If you don't have a sugar thermometer, you can test whether the jelly is ready by placing a drop onto a cold plate (put the plate in the fridge prior to starting to cook). If the jelly is ready, it should rapidly form a skin and the surface should wrinkle if touched. While the jam is cooking, you can sterilise your jam jars in the oven.

4. Remove the pan from the heat as soon as the setting point is reached, skim off any scum and pour into warm sterilised jam jars. Pop a disc of wax paper over the jam and finish with a jam pot cover. When the jam has cooled, the jars can be labelled.