Further up thread it was questioned how such a 4-month rule could be enforced. I suggested that it can be enforced by the general public showing, or speaking, their disapproval if they see an obviously elderly person out on the street.
From this thread it can be seen that this sort of pressure can quite easily be applied. Already some posters are implying that those who are not willing to go into isolation for 4 months will be guilty of wasting the NHS's time and precious resources, of being selfish, idiotic, etc, etc.
It appears that we are already in a situation where the government is panicking. Having starved the NHS of staff and equipment, we are now in a situation where, even if we had anywhere near enough respirators (which we apparently don't) we don't have enough staff - and it was reported that many staff are not trained in the use of respirators. So people over 70 who are not willing to completely isolate themselves for 4 months and who sadly succumb to the virus must be portrayed as being foolish/stubborn/selfish and bearing the primary responsibility for their own illness/death, rather than a different narrative - "we couldn't treat them properly because we didn't have enough nurses, beds or staff" - being presented.
Of course, this is an unprecedented and unknown health threat and every country will have great difficulty in having sufficient resources to manage it. However, as I said before, those working on the front line - doctors, nurses, paramedics, support staff - have been saying for several years that, should a major health emergency occur, the NHS would be unable to cope. Despite the undoubted hard work and goodwill of its harried staff, even before this crisis there were many reports of bed shortages and ambulances that were taking hours to arrive.