The above illustration is of the British Crown Jewels as we know them now, but there were predecessors, long gone now, thanks to the efforts of Oliver Cromwell, who had no truck with such baubles.
We are inclined to forget that there was a Welsh crown too, until it was seized by Edward I in 1283. The picture immediately above is of Llywelyn ap Gruffydd, Prince of Wales, crowned and seated beneath his arms. It is not contemporary, but is set when he paid homage to Henry III in 1267.
The next illustration above is from the 16th century, and shows the arms of Wales, surmounted by a crown of unusual design. Llywelyn’s crown was still around at this time (pre-Cromwell) and so this may well be an accurate depiction of the crown that Edward I seized in 1283.
Llywelyn’s crown (Talaith Llywelyn) was left at Cymer Abbey (together with other priceless items) at the start of Llywelyn’s final campaign, but was seized by Edward I when Llywelyn was killed in 1282.
The death of Llywelyn and his grave at Cymher (Cymhir) For more about the abbey, see https://en.wikipedia.org/wiki/Abbeycwmhir
Taken to Westminster Abbey, it was presented to the shrine of Edward the Confessor as a symbol of the crushing of the Welsh. Before this presentation it was coated in gold to make it look more impressive, which the contributor to Wikipedia thinks is an indication that the original was perhaps made of iron.
It remained in Westminster Abbey, until transferred to the Tower of London at the beginning of the 14th century. It remained in English hands until Oliver Cromwell came along, warts and all. Or rather, it does not appear to have still been present when he melted down the Crown Jewels. Where had it gone? And when?
Tapestry showing Arthur, circa 1385
No one knows the age of this lost crown, or what else was left with it at Cymer Abbey. However, when it was all seized by Edward I, the crown of King Arthur was said to have been among it. This latter crown was believed to have been forged much earlier. Now, whether the “crown of Arthur” is a general term for principality of Wales, or refers to the actual crown of King Arthur is not known. And there is some confusion as to whether this crown of Arthur was actually the same item as Llywelyn’s crown. One and the same crown. If it was indeed the crown of King Arthur. It was truly priceless.
Maybe it still is, if we knew where to look. . .
In the meantime, Llywelyn ap Gruffydd is still remembered. See https://alchetron.com/Llywelyn-ap-Gruffudd