A bottled sauce based on vinegar, anchovies and garlic with cayenne pepper and soy sauce and mushroom or walnut ketchup. It may be coloured red with cochineal. It is then infused for up to a month and may be used to add to sauces or gravies to give additional savoury flavour. My Cassell's Dictionary of Cookery from 1898 calls this Harvey's or camp vinegar.