The reporting on this is quite hard to follow I find.
I'm getting the following; basically the UK government was using a model and inserted some variables which someone at Imperial realised had been shown to be too low and that inserting the correct values for those variables meant the UK strategy would lead to a quarter-million deaths. The UK government accepted their error and are changing their strategy, hence today's announcements. Is that correct?
Definitely not the way I take it. Last Thursday they already knew there would be that many deaths from what they were suggesting (indeed that ghoulish CMO said it might be 500,000), and were happy to push ahead with herd immunity strategy as govt policy. Then over the weekend there was massive pushback at this insanity, and Hancock tried to row back, saying that herd immunity wasn't the strategy but just a 'scientific concept'. Now, miraculously, they've decided to do roughly what other European countries are doing, with 1/10 the expected death toll. And hopefully less.
This is nothing to do with Imperial - this is just a cover to say that they are 'following science' again - or an error, and everything to do with the fact they've realised they can't get away with what they originally intended. Or lost their nerve, I dunno.
They're trying to cover for the fact that they have done a massive 180 degree turn. Not to say that they won't try to revert to a madder strategy at some later stage, tho