This piece, describing some political movies by the late Queen Elizabeth II, claims that her her predecessor Queen Elizabeth I Tudor spoke Welsh at the English court. Did she really?
While the Tudors were famously of Welsh origin, Elizabeth I was five generations removed from her Welsh ancestor Owain Tudur, which makes intergenerational language transmission seem unlikely. Due to the low status of the Welsh language among 16th-century English high society, I would not expect that Welsh-language textbooks were widely circulated or that finding a Welsh tutor for Elizabeth was a major concern.
Why is it believed that Elizabeth Tudor spoke Welsh? Are there other instances of early modern English nobility learning Welsh as a second language?
The reasons people believe Elizabeth I spoke Welsh are circumstantial. One of her closest courtiers from an early age - Blanche ferch Harri - was Welsh. She served Elizabeth as an infant and she was probably with Elizabeth when she was imprisoned in the Tower by Mary and remained almost constantly by her side until her death in 1590.
That doesn't prove anything in and of itself and English policy towards Welsh was hostile at the time. The 1535 Laws in Wales Act (two years after the birth of Elizabeth) said officials who used welsh could forfeit their office so how much welsh a courtier would teach a princess in that climate is up for debate.
also that from henceforth no Person or Persons that use the Welch Speech or Language, shall have or enjoy any manner Office or Fees within this Realm of England, Wales, or other the King's Dominion, upon Pain of forfeiting the same Offices or Fees, unless he or they use and exercise the English Speech or Language.
However, we do know that Elizabeth spoke and wrote a large number of languages (at least French, Latin and Italian). She made translations from and to French, Latin and Italian. She reportedly spoke Spanish though didn't use it for political reasons and she made an attempt to learn some Irish - she commissioned a beginner's guide to Irish in preparation to meet Irish chieftain Seán Ó Néill.
London-based Venetian diplomat Giovanni Carlo Scaramelli said she spoke 9 languages, which included Welsh, Cornish, "Scottish" (Gaelic) and Irish at a native level. Scaramelli didn't speak those languages though and he was writing shortly after her death so it's likely an exaggeration (it's unlikely she spoke native-level irish for example) but also tips the balance towards her speaking some welsh and implies Elizabeth being able to speak welsh was a widely-held belief during her reign*.
Elizabeth also softened English policy towards Welsh - encouraging the liturgical use of Welsh - which led to William Morgan's translations of the bible and book of common prayer.
Not a massive amount of Welsh was written during the early modern period compared to a couple of centuries earlier or later so it's not a surprise there's no welsh writing from her even if she did speak welsh (the welsh literary renaissance that began a century or two later arguably had its roots in Elizabeth's reign).
So it's highly likely she spoke some welsh, and at least possible she spoke welsh fluently and did so from an early age.
* it's worth saying that overstating the linguistic abilities of royals is a practice that continues to the present day. Lots of people call Charles III and Prince William "welsh speakers" on the basis of learning a small amount for a speech or two.