From The Crown Jewels 1998, concerning the crowns of Queen Alexandra and Queen Mary:

The eight half-arches are in the Continental, not the English, tradition. Two arches (or four half-arches) had been the norm in England since the Restoration. The multiple arches may have been adopted in homage to Queen Alexandra’s Danish origins; she must have been well acquainted with the Crown of King Christian V of Denmark which had been made in Copenhagen by Poul Kurtz in 1670; this has the same number of arches.
There is little question but that Queen Alexandra’s Crown inspired George V’s Imperial Crown of India (the Delhi Durbar Crown...) and Queen Mary’s Crown, both made in 1911.