New light is being shone on the British royal family's 400-year association with Japan after fresh research into the former's extensive holdings of artworks.

Curators have been studying more than 1,000 Japanese pieces and, for the first time, have been able to establish the provenance of several key items thanks to new information.

Many of the standout objects in the collection were gifts to mark visits, coronations and treaties. Direct interaction between rulers only really happened after Japan reopened to the West in the 1850s after a period of seclusion from the 1630s.