You seem up set.
The paper does say 500,000 but then goes on to say that prediction is unrealistic, it makes a lower estimate based on likely scenarios, The worst case realistic scenario is about half that figure. It you read the paper it makes sense. If you pull out meaningless sound bites then it doesn't.
Also we did undertake measures to prevent that worst case. So you cannot say what would have happened if we had not initiated measures to control the virus.
Again that figure of 50,000 cases does seem high. I did not see the interview. Was he talking about new cases or active cases? For new cases it sounds high. So far we've not seen anything like that (although I suspect we had a lot more cases than we recorded particularly at Cheltenham). If he's talking about active cases then that might be possible.