Discard any blemished berries and pack the sound ones into a large pickle jar. Put all the remaining ingredients into a saucepan, bring slowly to the boil and simmer gently for 10–15 minutes. Strain over the bilberries. Cover the jar with a plate, putting a weight on top to keep the fruit down if necessary. After 3 days pour off the liquid and reboil it. Pour it on to the berries while hot. Seal the jar when the contents are cold.