The "occult ritual" you are referring to was actually a part of the 1946 National Eisteddfod of Wales, the most important annual cultural gathering in the principality, and the largest cultural festival of its kind held anywhere in Europe.

This was the year in which the princess (she became queen only in 1953) was elevated to the rank of bard, and the ceremony that was filmed at that time, and which you've seen, was a part of that process. It was carried out by "druids" who were members of the Gorsedd [community - literally "throne"] of the Bards. Ceremonies of this sort are actually fairly regularly held to honour major contributors to music, poetry and the arts in Wales; the elevation of Elizabeth to their ranks was, of course, purely honorary.

Now, it's important to add to all this that the eisteddfod, in its modern guise, is not an age-old festival. Cultural meetings of this sort certainly were recorded as early as 1176, when an eisteddfod was organised in Cardigan by the Lord Rhys, a noted ruler of Deheubarth (an independent principality in what is now South Wales), but even these date to more than a millennium after the Romans arrived in Britain. Moreover, there is also no evidence of continuity between the festivals of the Middle Ages and those of the modern period. What we can see in the film of Elizabeth's elevation is merely the romantic recreation of an invented tradition.

Similarly, while an eisteddfod is deliberately designed to project an image of cultural continuity and assert the ancient uniqueness of Welsh culture, its druids are not direct lineal descendants of pagan priests who were practising similar rituals when the Romans arrived in Britain. The first meeting of the Gorsedd actually took place only in 1792, and it was held not in Wales but at Primrose Hill in London. The originator of the order was Edward Williams, better known by the Welsh name he created for himself, Iolo Morganwg (which, translated, simply means "Neddy of Glamorgan") – an autodidact stonemason, antiquary and forger of Welsh history from Cowbridge who was a devotee of Arthurian literature and a part of the Romantic movement that flourished across Europe from around 1780. Williams – whom Geraint H. Jenkins has described as "arguably the most extraordinary figure in the entire cultural history of Wales," and Prys Morgan as the perpetrator of "an amusing confidence trick" and creator of "a kind of supporters' club for the language, literature and history of Wales" – was not merely a forger. He seems to have actually convinced himself that he and a friend, Edward Evans, were the last remaining survivors of an "apostolic succession" of bards dating back millennia. The pair hoped to use their "bardic revival" to assert a cultural identity for Wales (in fact, specifically for what were by then the already heavily Anglicised counties of South Wales), but Williams did this by creating what were in fact spurious links to an imagined past. The first time that the Gorsedd of the Bards participated in an eisteddfod was in 1819.

So, as has been pointed out, while Williams claimed to have recovered information about Wales's ancient druids and their "Bardic alphabet" and rituals as a result of his scholarly researches, the reality was that the Gorsedd

was a fantasy, of course, as scholars have found many of Iolo's works to be. Yet the body of bards he established resonated with the Welsh people. It gave them an institution which esteemed and cherished the language, something which hadn't existed since the Age of the Princes hundreds of years earlier.

The ceremony filmed in 1946, then, was less than 130 years old and – very ironically, given its focus – had been designed to assert a Welsh identity distinct from that of Wales's oppressors, the kings and queens of England.

Sources

Marion Löffler, The Literary and Historical Legacy of Iolo Morganwg, 1826-1926 (2007)

Ffion Mair Jones, 'The Bard is a Very Singular Character': Iolo Morganwg, Marginalia and Print Culture (2010)

Prys Morgan, "The hunt for the Welsh past in the Romantic period," in Hobsbawm and Ranger (eds), The Invention of Tradition (1983)