The Snowdonia National Park Authority decided in November 2022 to use the Welsh names Yr Wyddfa (for the mountain Snowdon) and Eryri (for the region of Snowdonia). This will apply ‘in both Welsh and English contexts’. https://snowdonia.gov.wales/paper-on-place-names-principles-approved-in-order-to-safeguard-and-celebrate-welsh-place-names-within-the-national-park/
According to a press report, the Authority will:
- in Welsh correspondence, use only Welsh names;
- in English texts, use the forms Yr Wyddfa (Snowdon) and Eryri (Snowdonia). This is because the use of the English names is set in law and they must be used in statutory documents. https://www.dailypost.co.uk/news/north-wales-news/yr-wyddfa-eryri-take-precedence-25534108
It will be interesting to see whether this change will lead to English speakers using the Welsh names.
For other posts on Welsh place names and on the official name of the Welsh football team, please see https://languagemiscellany.com/tag/welsh/