Alegar by John Spottiswood.

Most of us know malt vinegar as the condiment that's always put on the table wherever British fish and chips are served. It's made from malted barley, and has a pungent, lemony flavor. It's a good choice for pickling (assuming it contains at least 5% acetic acid), though it will darken light-colored fruits and vegetables. It's also the vinegar of choice for making chutneys. Since it's so assertive, it's not a good choice for vinaigrettes or delicate sauces. Varieties include brown malt vinegar and distilled malt vinegar, which is clear.