There was a view that adopting a herd approach ("taking it n the chin") could have seen figures in that ball park if the virus remained unchecked.
There are nearly 12 million (11,989,322) people aged 65 and above in the UK of which 5.4 million people are aged 75+, 1.6 million are aged 85+, over 500,000 people are 90+ (579,776) and 14,430 are centenarians.
It doesn't take too much imagination to see how so many people could be at risk.