As is usually the case, the possibility that the action may well have been successful is, in a sense, being used as evidence against it. In the last week, the number of daily deaths has appeared to level off. I can't claim that this is definitive evidence that Lockdown 2 has had an impact, or discount the possibility that this was due to Tier 3 measures leading up to it. But it defies common sense to suggest that, left unchecked, the trajectory of the disease would have been exactly the same.
Back a month ago, when we were asking how many Covid-19 deaths would be an "acceptable" loss, I'd suggested that around 5,000 total in the period from October 15th-December 25th would mark a relative success, and later revised that up to 10,000. We passed that total yesterday. In that sense, the Government acted far too late, if anything.