The Queen pretty much always sticks to one wardrobe rule - wearing plenty of bright colours!
But there was a rare occasion when she chose to wear black instead of her usual bold hues - and it happened 40 years ago to this day.
MORE: The Queen wows in pastel pink for radiant public return, and fans are in love
Her Majesty and the Duke of Edinburgh met Pope John Paul ll in 1980 during their first visit to the Vatican, with the Queen wearing an elegant black gown and a traditional matching veil.
WATCH: Countess Sophie comments on the Queen's colourful wardrobe
She also chose the beautiful Vladimir tiara for the special occasion, with its stunning pearl drop details - which is widely thought to be Her Majesty's favourite headpiece.
The Queen wore a black gown to meet the Pope in 1980
Usually, the Queen is only really known to wear black when in mourning or for Remembrance occasions.
It is traditional for women to wear black when meeting the pope, though royal women who are Catholic are granted the 'privilège du blanc', meaning they are permitted to wear a white dress and veil during the meeting.
Princess Charlene wears white during meetings at the Vatican
Other royals who have worn white to meet the pope include Queen Letizia of Spain and Princess Charlene of Monaco.
MORE: Kate Middleton pays sweet fashion tribute during adorable new video
When the Queen visited the Vatican again in 2000, she again chose a black outfit and a hat with a veil - though many were surprised when she opted for a lilac ensemble for her trip to meet Pope Francis in 2014.
The Queen wore lilac at the Vatican in 2014
In fact, Pope Francis does not now enforce dress code rules for women during private audiences. Since then, the Duchess of Cornwall has also visited the Vatican wearing cream, instead of the traditional black.
Her Majesty pictured wearing grey in 2016
Another occasion when our monarch surprised by wearing a darker hue was during her appearance at King's Lynn station in 2016, when she was pictured in a deep grey coat with embellished details.
We'd argue it's not quite black, however, though it was certainly a departure from her usual pastel and primary colours…