Chop the onion coarsely into small pieces roughly ¾ cm in greatest dimension.

Macerate the daikon with the salt for about thirty minutes, then rind and squeeze it dry.

Pan-fry the onion in a little oil over moderate heat until just translucent then add the sugar and vinegar.

Simmer until the daikon is just turning translucent but remains crisp-tender.

Turn the heat to high, add the HP Sauce and reduce the sauce to a fairly syrup glaze.

Cool and transfer to a suitable container. Refrigerate until needed.