Simmering the chicken in malt vinegar softens it and the sourness evaporates, leaving a refreshing flavor. (From the Head Chef at the British Embassy in Tokyo.)
The British Embassy in Tokyo ran a campaign "Food is GREAT: A Taste of Britain" to introduce British cuisine. Check out their Facebook page:https://www.facebook.com/oishii.igirisu
Malt vinegar is the kind usually used in British cuisine. It goes well with fish and chips and many other dishes too.
Enjoy Japanese food around the world.