From today, an unexpected phone call from a new number may be more than just a nuisance. The UK’s test and trace system has launched and will ask those who have been in close contact with someone who has tested positive for Covid-19 to self-isolate for 14 days.

Owl’s view is that it has been launched prematurely so as to distract from Dominic Cummings. Boris is playing dangerous games.

By Daniel Capurro, Telegraph Front Bench Editor

The news was announced by Boris Johnson during his appearance in front of the Commons Liaison Committee, at which he also faced a grilling over the Dominic Cummings affair.

Laura Donnelly, our health editor, explains the full details of the system and how it will work here. For now, the crucial question is: how ready is it?

The woman in charge of the scheme, Baroness Dido Harding, admitted yesterday that it would be some weeks before the system is “world-class” but claimed that it would get “better and better” as we head towards the autumn.

– Civic duty doesn’t put food on the table –

There’s always the possibility of the unexpected, but at the moment the doubts surround several key issues.

The first is that the system is voluntary. While Matt Hancock, the Health Secretary, and Johnson have both warned that they will make quarantining compulsory if necessary, that could prove incredibly difficult to enforce for potentially hundreds of thousands of people at a time. Fines could go some way to maintaining compliance, but ultimately it will come down to individuals.

The Government is clearly trying to frame self-isolating as a civic duty, but as with lockdown, the reality is that it will only be as effective as the systems in place to support those who need to self-isolate. The need to go into quarantine will be sudden and immediate and it’s entirely plausible that it could cover the majority of someone’s social and support network.

In those circumstances, how does someone pick up their children from school or get food for a fortnight? And will their employer be supportive of their need to quarantine?

– A big dose of trust –

The UK is also not going down the route of some Asian countries of having quarantine centres where those who test positive must stay. That is seen in government as incompatible with British culture and personal freedoms. But for anyone not living in a large home, it means they are likely to infect their family members too.

Another big hurdle the system faces is trust. If you are contacted and told to self-isolate, you will get tested for the virus. But even if you test negative, you will still have to complete the full fortnight of isolation because those who are yet to display symptoms may test negative falsely. That is going to be a hard message to get across.

The biggest fear, alongside compliance, is that the system simply won’t be fast enough. For one, Britain doesn’t yet have enough rapid testing capacity, meaning people could be left waiting several days for a result. But also, the NHS’ contact tracing app is not yet launched. While the app is only an aid, without it contact tracers can only work so fast.

– South Korea lite –

And again, the Government’s reluctance to embrace East Asian-style systems because of (legitimate) civil liberties concerns will make the system less efficient. In South Korea, contact tracers have access to CCTV, credit card transactions and GPS data.

That will slow the work of contact tracers, but it will also increase the reliance on the British public to be honest. There has been much focus on the potential for malicious use of the system, but perhaps the bigger risk is that people are reluctant to admit to all their contacts for fear of costing their friends and family employment.

Again, the support will need to be in place to make sure that no one is having to make an undue sacrifice by self-isolating.

– Still a big moment –

It’s not impossible to make such a system work without going into full surveillance state mode. Germany, for example, has been successful so far with a system far closer to Britain’s. But clearly there are issues, seen and unforeseen, that will need fixing on the fly.

Yet for all the potential problems, the significance of this moment should not be lost. Today, the Government will officially review the UK’s lockdown and its coronavirus alert level, which Johnson is believed to be planning to reduce to level three.

The test and trace system, should it hold together, is what will enable the country to move from a crushing national lockdown to relative freedom for the majority, and only short-term lockdown for a specific few.