The princess, formerly Lady Diana Spencer, wore the family heirloom for her wedding to the Prince of Wales in 1981, and many times afterwards.
The piece has an elaborate design of stylised flowers decorated with diamonds in silver settings.
It was looked after by William’s uncle, Earl Spencer, until William and Harry both turned 30, when it was inherited by the princes.
Earl Spencer once recalled how the tiara gave Diana a splitting headache on her wedding day because she was not used to wearing it.
The Duchess of Cambridge has yet to wear the Spencer Tiara.
Grand Duchess Vladimir’s Tiara
This imposing tiara features 15 interlaced diamond circles with large pearl droplets.
The pearls can be taken out and replaced with emeralds or it can be worn ‘widowed’ – without drops.
Tsar Nicholas II’s aunt, the Grand Duchess, hid the piece in the vault at Vladimir Palace in 1918 when she fled St Petersburg in the wake of the revolution.
It was found by a member of the British Secret Intelligence Service who smuggled the jewels out of Russia for the Grand Duchess.
It was later sold to Elizabeth II’s grandmother, Queen Mary, and was then eventually inherited by the Queen. It has also been worn by the Duchess of Cornwall.
The Oriental Circlet Tiara (also known as the Indian Tiara)
This was a favourite of the Queen Mother.
The large but delicate-looking piece features diamond lotus flowers and arches, and wraps itself nearly all the way around the wearer’s head.
Prince Albert had it made as an opal tiara for Queen Victoria in 1853. But Queen Alexandra later replaced the opals, which were thought unlucky, with rubies.
Queen Mary’s Fringe Tiara
The Queen wore Queen Mary’s Fringe Tiara when she married the Duke of Edinburgh in 1947.
First worn as a tiara by Queen Victoria in 1839, the diamond fringe would connect Meghan to royal family history and to a successful royal partnership that has lasted more than 70 years.
Strathmore Rose Tiara
A demure choice would be the pretty Strathmore Rose Tiara, which belonged to the Queen Mother and was a present from her parents in 1923.
It can be worn on top of the head or across the forehead as a bandeau.
The delicate floral design has not been worn in public for many years.
Queen Alexandra’s Russian Kokoshnik Tiara
If Meghan wanted to go all out and pick one of the largest tiaras, she could opt for this impressive fringe headdress.
Formed of 61 platinum bars and bejewelled with 488 diamonds, it was a gift to Alexandra on her silver wedding anniversary in 1888 and is based on a Russian-style peasant girl’s headwear which was in fashion at the time.
Queen Mary’s Girls of Great Britain and Ireland Tiara
This is an unlikely choice. One of the Queen’s favourites, the tiara is synonymous with the monarch and she wears it often.
Meghan is also expected to steer clear of tiaras that Kate has worn.
The duchess’s wedding tiara was the little known Cartier Halo Tiara – also called the Queen Mother’s Scroll Tiara – loaned by the Queen for her 2011 nuptials.
It was made by Cartier in 1936 and bought by the Queen’s father, then the Duke of York, for the Queen Mother, then the Duchess of York.
Kate has also worn the Queen Mother’s Papyrus Tiara – also known as the Lotus Flower Tiara – made of diamonds in fanned motifs crowned by floating diamond arches.
The duchess’s other go-to tiara is Diana’s favourite, the Cambridge Lover’s Knot Tiara, a diamond and pearl-encrusted headpiece made in 1914.
The item shows a strong French influence in its neo-classical design of 19 diamond arches, each cradling an oriental pearl drop.
It was given to Diana by the Queen as a wedding gift in 1981.
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