The Queen received the King and Queen of Tonga at Buckingham Palace. She also held an Investiture.
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This is a lot of brooch power for an audience - nice to see Her Maj bringing out the (relative) big guns for a fellow sovereign! Any sighting of Queen Adelaide's cluster of diamonds is a welcome sight. Tupou VI is visiting London in advance of his coronation next year; he came to the throne in 2012.