The one and only rationale for lockdown 2 is to prevent the NHS becoming overwhelmed. No one cares about deaths. They aren’t even pretending to any more. They just care about avoiding the situation of images on TV of patients lying in corridors in hospitals.
And they are operating on a worst case planning basis. It is now well established that there was a blatant attempt to frighten the public by using fake figures for the numbers of projected deaths.  The scare tactic was a “scenario” i.e. just a possibility – for which there was no statistical evidence. 
Observers of how the corporate-government world works will not be at all surprised to see the “scientific data” being fixed to support the predetermined political-financial aim. This is how the system works.
The situation is wholly unnecessary. They have had 6 months to build more temporary hospitals. This can be done in a few days. True; field hospitals also need to be staffed. But in 6 months it would have been possible to put together a workforce – without poaching staff from hospitals. (For example; army medics, final year nursing students and people hired from overseas. In 6 months people could have been trained to work as auxiliary nurses as well). That they didn’t do this simply reflects the complete absence of proactive planning which has characterised the inept and dangerous response of this government. Now they are blaming the public – an extraordinary temerity. [Update: There are some claims now coming out of the Health Service that the problem with the Nightingale Hospitals is that they can’t find the staff for them. This is why despite the huge costs of building 7 such facilities they have hardly been used. Assuming this is true, and my guess is they didn’t try very hard, even so there remains a question (quite apart from the rather obvious point – surely this could have been foreseen?); could they not use these hospitals as dedicated treatment centres for Covid patients meaning that they could prevent the problem of people catching Covid in hospital – which is a major problem? Altogether it seems that the government are running this show just thinking that if they throw vast sums of money at some private sector companies somehow this will fix the problems. It seems they don’t realise the situation calls for something different. That is serious thinking and planning based on reality not just spraying cash around. It seems that government, ministers and senior health officials, just don’t have this capacity.]
Currently there is no great pressure on hospitals. They are really planning for the worst possible imaginable case.  They can accept zero risk.
The reason for the new lockdown is to prevent any risk at all of the NHS going over capacity. The reason for this is political not medical. The reason is that images on TV of sick patients lying in corridors and/or news reports of people dying because of a lack of ventilators is completely politically unacceptable. Recall the amount of airtime and political mileage which was made out of a single child sleeping (not dying) on a hospital floor at the last election. Even 10 people struggling to breathe on stretchers in a corridor would end multiple political careers.
“Protect the NHS” really means that. But is also means “protect our political skins please”. 75% of the population support this new lockdown. This means that 75% of the population have been taken for complete fools.
You cannot coerce 60 million people into obeying the restrictions. You need people to voluntarily follow them. The government might have been able to secure this compliance by setting a good example, by introducing restrictions in a planned way (not reactively) and by explaining the need for them honestly. They’ve done the opposite; they failed to set a good example (Cummins). It must be obvious to everyone that the government has no plan. And they have have tried to frighten people into compliance rather than explain the problems in an honest way. The failure to involve local government has been a major failure. People might have responded better to messaging communicated at a local level.
At this point all bets are off. The only way that an epidemic of this kind could be contained would be if the vast majority of the population voluntarily acted in a responsible way. But at this point we can say that the situation has degenerated into a negative parent-child relationship; a series of restrictive measures enforced by a punitive system of fines imposed on an recalcitrant public. 75% of the population say in surveys that they support the new lockdown but overall observance of the necessary measures – such as self-isolation (less than 20%)  and social distancing seems very weak.  If you are in the position as they are now of trying to threaten people with more coercive action they have already lost.
(Another undoubted factor in the latest uptick of the virus has been the general relaxation of the population after the first phase of restrictions ended. A relaxation no doubt encouraged by the virtually insane “Eat Out to Help the Virus Out” scheme cooked up by the government – in yet another populist attempt to create a feel good factor).
As matters stand it looks like the UK is in the worst possible space. In effect the virus is not being controlled despite hugely damaging lockdowns; lockdowns which are likely to lead to thousands of deaths as a result of the non-treatment of ordinary conditions  and which cause huge economic damage – either by closing businesses or by the mushrooming public debt resulting from the furlough and other support schemes. It is difficult, objectively speaking, to see how a more inept response could have been imagined.
Another clue to why there is a new lockdown may be given by this anonymised report in the Telegraph:
Earlier today medical experts also warned that Nightingale hospitals are not the solution to easing the burden on the NHS’s intensive care units as cases continue to rise. Two senior intensive care specialists said opening field hospitals to help the health service during the second peak of coronavirus puts pressure on the system and risks poaching staff from already over-burdened hospitals.
I think this may be a classic case of a local authority (and the thinking of the NHS senior managers will be of the same mindset as a local authority) deciding that the most important thing is to protect their monopoly. They can’t deliver the necessary health care but they are going to make d*** certain that no one else does either – so they can protect their monopoly. This seems to be where we are right now.
What this looks like is an unholy alliance between government ministers determined to keep their jobs and NHS bureaucrats determined to protect their kingdom.
In their desperation to “Protect the NHS” the government and senior civil servants in the health system have killed tens of thousands of people. They killed 16,000 by releasing untested Covid-19 infected people into care homes in February, March and April thus, in the words of one consultant, seeding Covid into care homes. They did this to clear bedspace in the NHS so there wouldn’t be TV images of people being treated in corridors.
As soon as the epidemic started GPs in effect shut their doors. A rather startling response some might think. The result in general of the lockdown, cancellation of routine operations (in part preventative to make sure that there was enough space for Covid patients and there weren’t any pictures on TV of people lying in corridors), and difficulties in getting a GP appointment has meant thousands of cancers have not been detected – which will lead to several thousand more deaths. 
In Russia hospitals are getting full. But they haven’t kicked old people out (to infect others). And they haven’t closed down their economy a second time. They are just doing what they can. This is a video (shown on a Russian website and by Yandex – so much for censorship) showing patients in a Moscow hospital lying in a corridor. There is an interview with the senior doctor in which he calmly explains the situation; people are still being treated and ventilated when necessary. There’s no panic and no hysteria. And they haven’t killed 20,000 people (as a very conservative estimate) to avoid such pictures being shown.
- https://www.telegraph.co.uk/news/2020/11/01/alarmist-covid-modelling-panicked-pm-lockdown-doesnt-pass-smell/?li_source=LI&li_medium=liftigniter-rhr https://www.telegraph.co.uk/news/2020/11/06/friday-morning-news-briefing-covid-death-toll-graphs-wrong/ https://www.telegraph.co.uk/news/2020/11/05/covid-graphs-wrong-death-toll-will-not-surpass-first-wave/
- https://www.theguardian.com/society/2020/jun/01/millions-in-uk-miss-cancer-screenings-tests-and-treatments-due-to-covid-19 https://www.theguardian.com/society/2020/nov/04/four-week-cancer-treatment-delay-raises-death-risk-study-nhs-covid