Of course, it was rampant political opportunism by Starmer but what some will doubtless take from it is his speed to do so. Boris has been notably slow to make vital decisions.
As I said earlier I do empathise with the hard balancing act he has had to make. This is a horrible mess to navigate. But when science tells you to act fast and it will save a longer shut down of the economy later to prevaricate and delay and do something much less effective instead is a mistake a prime minister in a pandemic will struggle to get over.
Unless he is very lucky and those who think this will plateau much lower than the first wave and we see that happen before he has no choice.
UNfortunately, Starmer is likely to have delayed any such lock down as Boris is not going to be seen to follow his advice/order. Doiung thar in the next few days is like admitting he is not running the country.
Starmer should have gone to Boris, suggested it and agreed to support him in doing it, Might have happened then.