Royal Regalia: The official royal dress code
Traditionally the linings of medieval coronation cloaks and some other garments, usually reserved to use by high-ranking peers and royalty, were made by sewing many ermine furs together to produce a luxurious white fur with patterns of hanging black-tipped tails.
Her Highness Princess Marie Louise is pictured at the coronation of Queen Elizabeth II with a slightly different cloak. As a granddaughter of Queen Victoria, she was the last member of the royal family to be styled ‘Her Highness’ and as such her crimson robe was different and not lined with the traditional ermine but a simple crimson silk velvet.
In practice, rows of sealskin spots on the cape designate the peer’s rank; dukes use four rows, marquesses three and a half, earls three, viscounts two and a half, and barons and lords of Parliament two.
Royal dukes use six rows of ermine, ermine on the front of the cape and long trains borne by pages.
Peeresses’ ranks are designated not by sealskin spots, but by the length of their trains and the width of the ermine edging on the same.
In the case of Princess Marie Louise, although a member of the royal family, her position was considered as a distant-cousin and too far removed to warrant the traditional regalia. Her position in the family was not that of a Princess of the United Kingdom but a Princess of Schleswig-Holstein, which she no longer retained when the family removed their German titles after the royal proclamation by George V.
As such, she was no longer entitled to the same robe and wore a simple crimson silk velvet train instead.