Hull the strawberries and put them into a preserving pan. Crush a few of the berries near the base and set the pan over low heat to draw the juices.
Add the sugar and stir gently over low heat until dissolved. Bring up to the boil. Boil rapidly for a set – about 10 minutes. Draw the pan off the heat and skim. Leave to stand for about 15–20 minutes so that the berries will be evenly dispersed. Ladle or pour into jars. Cover with waxed paper circles when hot and seal when cold.