The Queen is rarely seen without a brooch on her lapel, usually worn to complement her strikingly bright outfits. But Her Majesty’s brooches are more than just pieces of beautiful jewellery: they symbolise deeper meanings and reveal significant aspects of the Queen’s life.

The Cullinan was found in a South African diamond mine in 1905 and remains the largest rough diamond ever discovered by Western archaeologists, weighing 3,107 carats.

The Queen has three Cullinan brooches, which were passed down to her from her grandmother, Queen Mary, in 1953.

These are the Cullinan III an IV brooch, the Cullinan V brooch, and the Cullinan VI and VIII brooch.

The first of the trio is the most valuable of all, estimated to be worth a whopping £50million, according to fine jewellery and engagement ring experts Steven Stone.

Queen Elizabeth II inherited the Cullinan III and IV brooch from her grandmother in 1953, but Her Majesty has barely worn the jewel since, according to the Court Jeweller.

However, the Queen did opt to wear it for a state visit to the Netherlands in 1958, and for a thanksgiving service at St. Paul’s Cathedral on the year of her Diamond Jubilee in 2012.

Charlotte, of 77 Diamonds, told Express.co.uk more about the Queen’s Cullinan collection, saying: “The Queen inherited these legendary diamonds from her grandmother, Queen Mary, in 1953, who adapted the Delhi Durbar Tiara to make the III and IV brooches in 1912.

“The Cullinan set also includes the largest clear-cut diamond in the world, the Cullinan I, which is mounted in the Sovereign’s Sceptre with Cross, while the second-largest is featured in the Imperial State crown.”

The Cullinan III and IV brooch is the most expensive brooch in the Queen’s jewellery box, but the Williamson diamond brooch closely follows it, estimated to be worth £25million.

The third most expensive brooch is the Prince Albert brooch.

This sapphire and diamond piece is thought to be worth £8million, according to Steven Stone.