Every British Royal wedding
Queen Victoria picked up a bunch on a visit to Germany to see her relatives; biosecurity rules were a bit laxer then (or Royals had diplomatic immunity) so she brought it back in her luggage and planted the sprigs up. The cuttings took, in the mild climate of her south coast palace, and grew into a shrub.
Her daughter Victoria cut stems from the shrub to use in her wedding bouquet; Queen Elizabeth II also cut stems from the same shrub for her marriage to Prince Philip. These were planted up later to propagate a second backup shrub. Princess Diana and Kate Middleton also included stems from this shrub in their wedding bouquets, to Prince Charles and Prince William respectively.
So myrtle has a nostalgic family connection for the British Royal family.
It also has a strong ancient connection to women and their power. Myrtle was the flower sacred to the Greek goddess Aphrodite, who rules love, beauty, fertility and sexuality. Myrtle was much used by the Romans in their wedding rituals, and during ceremonies at the annual festival to goddess Venus, Aphrodite’s counterpart. The flower symbolised the strength and power of the female.
Interestingly, the Jewish faith considers myrtle a masculine, not feminine, plant. Sprigs are given to the groom after the marriage and before the wedding night, to symbolise his virility.
So myrtle has long been associated with love, sexuality, and immortality – because true love should last forever.