Many thanks for taking the trouble to give us the time segments for this interesting video Dave. Not everyone has the time to watch the entire video so I am sure others, like me, appreciated the times you gave.
Princess Margaret
I have no idea about her brooch. I don't recollect seeing it previously.
Princess Anne
The brooch Princess Anne wore is, I believe, the bow brooch which Prince Charles is said to have given to her as a wedding present..
At the wedding,
Detail
Tiggy Legge Bourke
At the wedding
I suspect that this striking choker may be a family piece as her sister has also been seen wearing it on occasion.
Below is another photo of Tiggy Legge Bourke wearing the choker.
Detail showing the central diamond section.