Sterilise your storage jars. Bring the kettle to the boil, then pour the water into the storage jars and leave for 2 minutes before emptying.
Put the cider and malt vinegars, water, peppercorns, allspice, mustard seeds, chilli flakes, sugar and salt into a stainless-steel saucepan and bring to the boil.
Peel and finely slice the ginger (you should almost be able to see through it), then add it to the pan with the sliced shallots and boil for 2 minutes.
Shred the red cabbage – I like mine roughly the width of a pencil, but with some sliced more finely – and place it in a heat-proof mixing bowl.
Pour the hot pickling liquor over the vegetables, then toss everything together. Ladle into the storage jars, seal and allow to cool, then refrigerate.