I’m not sure either! British Rail was literally, factually privatised and sold off to a lot of different private companies, over a few years running up until 1997. It has not been re-nationalised since. I can’t understand how you wouldn’t be aware of that, unless your view on what nationalised and privatised means is different than the news/dictionary/encyclopaedia/anyone else.
The railways were nationalised between 1948 and 1997, but it’s currently 2023 - and unless you’re from a parallel universe where Neil Kinnock won, they haven’t been nationalised for two and a half decades now.
Worth taking statistics with a pinch of salt, but apparently after a couple of decades of underperforming privatised service, the UK population is overwhelmingly (across both sides of the political spectrum) in support of re-nationalising the railways.