A good summary with links is here: https://www.the-scientist.com/features/counting-the-lives-sa...
> On a more positive note, Ferguson and other researchers at Imperial College London published a model in Nature around the same time estimating that more than 3 million deaths had been avoided in the UK as a result of the policies that were put in place.
3 million people is ~5% of the entire UK population. Even using the high end of COVID IFR estimates (2%, from northern Italy), it would have required everyone in the UK to get COVID twice with no natural immunity to reach that kind of death toll.
Also:
> The most effective measure, they found, was getting people not to travel to work, while school closures had relatively little effect.
That article appears to agree with this one.