I had never noticed these additional diamonds, but that makes sense: as this tiara is a full circlet (as opposed to a "normal" tiara, open at the back), narrowing the diameter at the base must have required to enlarge the diameter at the top. The additionnal diamonds were added to avoid "holes" in the upper part of the altered tiara's design. It was very skillfully made.
Aigrette, I agree with your first paragraph, not with your second: I think the removal of the top line of diamonds was the consequence, and not the cause, of the narrowing of the tiara base. In other words, I don't think the Durbar tiara was altered because the Queen needed a few extra diamonds for another jewel.
A more plausible option is that the removed diamonds were re-used in the Durbar tiara itself, to make the small rosettes and additional diamonds identified by Martina.
--Previous Message-- : Many thanks Martina. I am intrigued by the : changes you have highlighted. Another : mystery for the board members to solve. I : hope we can do so. : : --Previous Message-- : : Kostenloses Bilderhosting : : In this comparison I highlighted some places : where diamonds have been added, so that the : diameter of the tiara would be increased at : the top. It must have been pretty : complicated to adapt the whole structure of : the tiara to a new shape. There must have : been at least the attention to wear it : again. : : : :