Queen Elizabeth II raises her hand during a downpour as she stands with (L-R) Prince Philip, Duke of Edinburgh and Prince Charles, Prince of Wales on the balcony of Buckingham Palace after the Trooping the Colour ceremony on June 16, 2007 in London. Each year the official birthday of Queen Elizabeth II is commemorated with a military parade and march-past of fully trained, operational troops from the Household DivisionPhoto by Peter Macdiarmid/Getty Images
And no, it's not a full mourning suit!
Queen Elizabeth II is one of the most well travelled heads of state in the world, having travelled constantly since she became queen in 1952. But did you know that she always travels with a bag of her own blood? And so too do Prince Charles and Prince William?
Read more: The Queen's advice to William and Harry
Speaking to Yahoo's The Royal Box, royal expert Duncan Larcombe said: "If it’s the Queen on tour, the royal physician is with them with a bag full of their own blood."
"Just in case something happens."
While it may seem odd, when you think about the importance of the Queen's health and how blood supplies might sometimes be questionable, it just makes sense to bring her own in case of an emergency blood transfusion. With the same applying to Prince William and Prince Charles.