The extension of the lockdown was understandable. Over the last week, however, fear created by talk of a second wave of the virus has fed pressure to extend the lockdown.
We are in a vaccine gap. That is not a comfortable situation for anyone. But we cannot stay locked down until a vaccine is found. The appropriate response to the gap is to unlock but to do so in a gradual and predictable way with checks and balances in place. That is what other countries are already doing. This minimises the risk of a second wave, while revitalising the economy.
Thus, science and economics must work together in determining our exit strategy. There is evidence of the present policy starting to unwind, with firms returning to work over the last week.
The lockdown measures are costly in economic and social terms. The economy has collapsed. As the lockdown continues, these losses may become permanent, with firms going bust and jobs jettisoned, and at an accelerated rate as time goes on. If we do not unlock soon, Britain could be the Western economy hit hardest by the virus.
Quality of life is impacted too. Mental health, domestic abuse and loneliness are rising. Cardiology and cancer treatments are delayed. This damage is avoidable if we start the process of unlocking.
But what about the second wave? The epidemiological models that underpin government policy are scientifically sound. But they do not explain how behaviour changes and assume that people behave in a fixed way. Yet, behaviour has changed. People adhered to the rules so well that the lockdown has been more effective than expected.
The fear of a second wave is a feature of epidemiology models that crucially depends upon the assumptions made. The maths of the models becomes more complex if the speed at which a virus spreads spatially across a country is important. But the basic drivers of the models are the same.
One is the assumption which is made on the degree of intermingling between infected and those susceptible to catching the virus. Another is the assumption about how many are infected by one person carrying the virus.
Small changes in assumptions can trigger very different views about the future. These assumptions will drive the policy which will impact our near-term economic future. While taking seriously the risk of a second wave, we must keep this fear in context. All the evidence is that it is not a fear to stop us unlocking, though we must be prepared for isolated instances when this virus, like others, reappears.
To minimise a second wave, testing and tracing must feature in any unlocking. A viable tracing app seems to be on the verge of being available. The key issue is how to persuade people to use it. To alleviate some worries, legislate that any information gathered by the tracking app cannot be used in civil or criminal proceedings.
Another safety feature of unlocking is that it is essential that behaviours continue to be different to before the crisis, both by people and by companies to safeguard their staff and customers. Behavioural change includes public hygiene through washing hands, social distancing and the wearing of face coverings, which should be mandatory on public transport.
Such coverings do not need to be surgical masks that threaten NHS supplies. They are to protect other people from you, not you from others.
Unlocking by geography has become a possibility because of the stance of the Scottish Government. There may be a case to experiment with unlocking completely on some of the Scottish islands, but on the mainland this is not really practical.
One geographical factor is crucial though. We can see from other countries that there may be purely local outbreaks after easing lockdown. The Government's legislative powers allow it to put features in place to deal with this swiftly, including devolving power if needed.
Unlocking based on age groups is not the way ahead and can be ruled out on behaviour, time and economics. The argument that 20-year-olds would be immune and not infect others would require impeccable behaviour and perhaps take months. Innovation from 20-year- olds will not fill the economic void. Also, it is not practical or desirable to place the nine million people over 70 under, in effect, house arrest.
It makes sense to unlock based on economic activity. Different sectors and types of business would open at different stages. Less risky areas first, risky areas last. Open spaces and less crowded areas first, enclosed or crowded last. Sectors like construction, with 2.3 million workers, would open early on. Mass sporting events should wait.
A traffic lights approach – Red, Amber, Green – to unlocking will mitigate the risk, is easy to understand, gives people hope and allows firms to plan.
As behaviours are key, red is the first stage – as people must still "stop" doing certain things they did before the crisis. Then amber as people must still be cautious, followed by green. Timelines for lifting stages need not be cast in stone but based on safety and effectiveness.
The trigger to unlock will come from the Government's five tests. It should then aim to be transparent about its aims.
Co-authored with Paul Ormerod, a visiting professor at University College, London.