royalwatcher:

Queen Elizabeth lent Princess Eugenie the Greville Emerald Kokoshnik tiara for her wedding day on October 12, 2018. 

Margaret Greville gifted her jewels to the Queen Mother when she passed away, who then left them to Queen Elizabeth when the Queen Mother passed away in 2002. The tiara was never worn by the Queen Mother or Queen Elizabeth. 

Photo by Pool/Samir Hussein/WireImage