Coronation Costume explains why both a tiara and coronet are worn, and how those tiny coronets stay put.

“ The coronets of peeresses, however, remained small, and for a doctrinal reason. It is only in comparatively recent years that the Church of England has ceased to insist on compliance with St Paul’s injunction to women to keep their heads covered when engaged in prayer. A peeress, at a coronation, does not put on her coronet until the queen herself is crowned, but it was inconceivable that she should be allowed to remain bareheaded through the earlier part of the service. The queen consort herself, when there was one, went to her coronation in the ‘diadem’ of gold, velvet and diamonds first made for Mary of Modena, worn by her and her successors and still preserved in the Jewel House. For her, with her attendant ladies to help her, it was possible to take off the earlier headdress before the imposition of the crown, but the peeresses, having no attendants, could do nothing of the sort. The regulations laid down, accordingly, that veils and tiaras should be worn, to constitute an orthodox head-covering, and the coronet should be small enough to be put on, when the time came, inside the circle of the tiara without disturbing it or the wearer’s coiffure. An ingenious device to be found on some peeresses’ coronets was the provision of small sliding rods, like miniature hatpins, which were permanently attached to the rim of the coronet. These, when it was put on, could be thrust home through the piled-up hair beneath, and would serve to ensure, to a great degree at least, the steadiness of the coronet and the wearer’s peace of mind. “