The pearls worn last night are not the ones I believe to be the Kuwaiti necklace with more graduated pearls. (See panel here.)
A comparison:
Rather, last night's double strand is the necklace I believe to be the Indian necklace with ruby clasp, often worn by the Queen Mother along with another single strand. (See panel here.)
These are not good views, but here are glimpses of the ruby clasp:
I didn't watch the entire ceremony so perhaps someone else can find a better view of the clasp.