Hello there Angela,
The modern Welsh National Eisteddfod traces its roots to the late-18th Century and its revival was due to the Gwyneddigion Society, of which Iolo Morganwg (Edward Williams) was a member. Iolo himself founded the Gorsedd Beirdd Ynys Prydain, which had a great influence on the ritual and aesthetics of the eisteddfod, however, he didn’t revive the modern eisteddfod per se.
When Henry VIII, ironically a Tudor – an ancient Welsh aristocratic family – ‘unified’ England and Wales, the Welsh language was not banned outright, but rather relegated to unofficial business, that is to say, legal proceedings, court hearings and so on had to be in English. The effect of this was basically to enforce a linguistic class system or hierarchy in which English, and therefore those who spoke English, were of a higher class and held in greater esteem. Despite this, and also thanks to Welsh literature – including an important Bible translation – Welsh was still in fairly rude health until the early 19th century, when it seems that the great social upheavals, movements of people, and industrialisation – especially in the south – were what started to see the language retreat. The Welsh (k)not, was used in some schools to discourage the use of Welsh among the children. I don’t think it was ever official British government educational policy, however, that does not change the fact that it was a cruel and crass expression of cultural imperialism all the same. Sadly, this was from atypical around the world in situations where a local language language or dialect was not the ‘prestige’ language of the state and government. Similar sorts of linguistic discrimination can be found all over Europe and elsewhere during the 19th and 20th centuries – until relative recently in historical terms.
Thankfully, we’ve moved on from those times, even though some rather nasty attitudes are still around.