Complex sentence: The first Scottish monarch to actually wear such a crown was James V, whose diadem was reworked to include arches in 1532, which were re-added when it was reconstructed in 1540, which remains the Crown of Scotland.
Split into simpler sentences: The first Scottish monarch to actually wear such a crown was James V, whose diadem was reworked to include arches in 1532. There were re-added when it was reconstructed in 1540 and this remains the Crown of Scotland.