Posters of original research, analyses, insights etc retain all rights to their work.
Such research etc cannot be used in any format without the written consent of the author.
Probably if Sarah's tiara not sold,Eugenie could use the tiara of her mother without any problems,in future, but not a tiara from the Queen :-) I had add some details of the diamond fringe tiara on the website Princess Beatrice wedding tiara -Queen Mary's diamond fringe kokoshnik