Wash the damsons and stone them. The easiest way to do this is to cut around the stone following the natural line in the fruit’s skin, twist one half of the fruit away from the other, then pick or lever out the stone. Core the apples (leaving the peel on) and finely chop them. Finely chop the onions and the garlic.Put the prepared fruit, onions, garlic, sultanas, sugar, ground ginger, salt and vinegar into a large pan. Take a small piece of muslin and wrap the allspice, cinnamon stick and wood avens root (or cloves). Gather the edges of the muslin together to form a bag and tie securely with string. Add the bag of spices to the pan, pushing it down into the vinegar, and set the pan over a medium heat.Bring the contents of the pan to a boil, then reduce the heat and simmer gently for about 3 hours, stirring occasionally especially towards the end of the cooking time to stop the chutney catching on the bottom of the pan.When almost all the vinegar has evaporated and the mixture is thickened, draw your wooden spoon through the centre of the pan. If the chutney is ready, the path of the spoon will leave a channel for a few seconds before the liquid flows in again.Remove and discard the bag of spices, then ladle the chutney while it’s still warm into sterilised jars, leaving a small gap at the top. Fasten the lids and leave to cool, then store the chutney in a cool dark place for at least 3 months before eating, to allow the flavours to meld and deepen.