The brooches were described as very modern clips mounted in platinum, triangular in shape with the initials G and M in aquamarines and diamonds. The brooches were delivered on the eve of the wedding and were worn the next day by the adult bridesmaids.
As far as I can see neither QEII or Lady Mary Cambridge were wearing one.
Has anyone ever seen other photos of the adult bridesmaids wearing these brooches? I don't recollect ever seeing QEII wearing anything which matches the description.
Unfortunately I cannot find a high definition photo of the bridesmaids.