I openly acknowledge that Nellie knows a great deal more about British royal jewels and gemstones than I will ever know.
When I read Nellie's post yesterday, I was excited by the possibility that the Koh-i-noor might have been used in the Delhi Durbar tiara.
Today, I expressed a tentative opinion. As I said, I was guessing -- Here is a quote from my earlier post: "Although I am only guessing, it seems to me that there would not be sufficient space to accommodate the the Koh-i-noor."
I suspect that it is the Cullinan IV set diagonally and that the use of flash has resulted in the edges of the diamond looking blurred and slightly obscuring, but not totally disguising, the straight edges of Cullinan IV. In that I agree with what Arthur said in his post today.
I stress again that my comment is merely a tentative personal opinion based on my limited knowledge. I am not pontificating.