Again, my understanding of it wasn't that they were just going to ignore all measures, only that they were only going to do them when it became necessary and at the right time when it is most effective. And they never actually said to do nothing. Only they didn't follow suit right away with shutting down schools or banning public events, etc.
If you don't already know by now, a lot of epidemiologists believe this may not go away in the summer. You have a highly contagious virus that is very difficult to contain. There is no vaccine to control it. Which is the idea behind getting some 'herd immunity'. A certain amount of tolerance to the virus in the population will potentially slow the spread right down. This idea didn't come from Boris Johnson.
Now it's too early really to know what will work best I suppose, but it is clear these ideas weren't just pulled out of someone's ass. lol
If you haven't already, watch this interview. You will have a better idea of the problems we now face.