Queen Mary and King Frederik will carry out their first ever state visit of their reign, travelling to Sweden from 6 to 7 May.
The Danish king and queen will be hosted by King Carl XVI Gustaf and Queen Silvia at a state banquet at the Royal Palace in Stockholm on Monday evening, where the dress code is likely to be white-tie.
Since her wedding in 2004, Mary has wowed us in four sparkling tiaras, but since her husband Frederik's accession in January, she now has access to more spectacular heirlooms from the royal jewellery vaults.
The Danish queen delighted royal watchers last week as she made her debut in the Danish Emerald Parure in the couple's first gala portraits.
The tiara, which is typically only reserved for the queen, was first commissioned in 1840 for King Christian VII for his wife, Caroline Matilda of England. Many of the emeralds featured in the headpiece are said to have been in the family since 1723.
The jewels cannot be taken out of the country and are displayed at Rosenborg Castle in Copenhagen, when it is not in use.
But which other tiaras could we see Mary wear in future?
Pearl Poire Tiara
The Pearl Poire tiara is part of a suite that became synonymous with Queen Margrethe during her 52-year reign. The diamond and pearl headpiece was commissioned as a wedding gift from King Frederich Wilhelm III of Prussia to his daughter, Princess Louise, upon her marriage to Prince Frederick of the Netherlands in 1825.
The jewels were inherited by Princess Louise's daughter, Queen Louise of Sweden and Sweden, and then later, left to her daughter, Louise, who was Queen of Denmark from 1906 to 1912.
The Danish Floral Aigrette
This striking headpiece can be worn in several different configurations, with Queen Margrethe wearing it on top of her head and as a hair accessory. Margrethe's mother, Queen Ingrid, acquired the diamond tiara in the 1960s and wore it for Margrethe's wedding to Count Henri Laborde de Monpezat in 1967. Margrethe later wore the headpiece for Frederik and Mary's nuptials in 2004.
The other four tiaras worn by Queen Mary
Danish Ruby Parure Tiara
Mary made her tiara debut at a gala dinner ahead of her wedding, wearing a 200-year-old diadem which was made for Désirée Clary Bernadotte (later Queen Desideria of Sweden) to wear for Emperor Napoleon's coronation I 1804. The parure also includes earrings, a necklace, a ring and a brooch.
Wedding Tiara
Mary was gifted a diamond wedding tiara from her mother-in-law, Queen Margrethe, which she has also worn with pearls since her nuptials.
The Edwardian Tiara
A fairly new addition to the Danish royal family, it was purchased at Bruun Rasmussen auction house in Copenhagen for €8050 in 2012. The tiara, which features diamonds, rubies and pearls, was first won by Mary to celebrate Margrethe's 75th birthday in 2015.
The Midnight Tiara
This contemporary tiara was made by Charlotte Lynggaard of Ole Lynggaard for an exhibition at Amalienborg Royal Palace Museum in 2009. The headpiece features diamond and moonstone berries with handcrafted leaves in rose gold, white gold and oxidised silver leaves. It caught Mary's eye and she first wore it for Prince Henrik's birthday dinner.