The government told us it would be all about data, not dates. But thus far each step in England’s re-opening has been precisely in line with the dates laid out by Boris Johnson back in February.

Indeed, in one sense COVID-19 policy seems to be more closely based on a set timetable than at any other point in the pandemic.

But might that be about to change? Because there are some warnings lights – not flashing red, but blinking all the same – that might give the government pause for thought about the final ending of lockdown on 21 June.

Now, when the government laid out its plans some months ago, it said that any decision over future re-opening would be based on four tests, which we’ll go through now.

Before we do, though, it’s worth underlining that for all that the government insists that this is an empirical process, it has been very vague about precisely what thresholds or levels of data would worry it.

In other words, we can make some guesses about the things that might provoke a decision, but they remain guesses, because the government hasn’t ever explained which kinds of data points would be in line with its plans.

Indeed, you could make the case, on a stringent reading of its tests, that it should already have paused the re-opening some time ago because of the rise of the delta variant.

With that said, let’s go through those tests in turn.

1. “The vaccine deployment programme continues successfully”

Here the evidence is promising. On the basis of data modelled by the Office for National Statistics, the proportion of adults who are now testing positive for antibodies to the virus is close to 80% in much of the UK.

The proportion having received their first dose is likewise at a similar level, while the proportion having received two doses of the vaccine is close to half in England and Northern Ireland and around 40% in Scotland and Wales.

By pretty much any standards, this represents an outperformance, both compared with expectations earlier in spring and compared with most other large countries around the world.

You can ask questions about whether coverage is high enough among certain age and ethnic groups and in certain areas, but for the most part the numbers here are incredibly encouraging. Tick.

2. “Evidence shows vaccines are sufficiently effective in reducing hospitalisations and deaths in those vaccinated”

Here, there are various data sources and here again most of the news is encouraging. A series of papers from PHE suggest the vaccines all reduce the risk of hospitalisation and death considerably for all the approved vaccines.

A glance at the overall hospitalisation data is similarly encouraging, showing that while hospitalisations of those aged under 65 are creeping up in recent weeks, there is no noticeable increase in those aged 65 and over.

Given this older age group accounted for comfortably the most hospitalisations in previous waves, this would seem to indicate that the vaccinations (the vast majority of this older group is now double-vaccinated) are having the desired effect. Another tick.

Since mid-May, the number of people aged 18 to 64 admitted to hospital has slowly gone up by 45%, from 42 to 61 daily admissions.

Only 35% of this age group has been fully vaccinated.

In contrast, almost all of those aged 80 and over have received two doses.

Admissions of the oldest and most vulnerable continue to fall. They’re down by 40%, from 11 people admitted daily in mid-May to seven in June.

In younger groups – where fewer people have had two doses – admissions are rising. However, the increase has been slower than in September (darkest line).

In regions with large numbers of the Delta variant, such as the North West, daily hospital admissions are rising faster in younger age groups than the national average.

3. “Infection rates do not risk a surge in hospitalisations which would put unsustainable pressure on the NHS”

Here the evidence is somewhat more worrying – though again it’s important to bear in mind the context. The number of cases around the UK is rising quite sharply – doubling every nine days.

This isn’t immediately obvious from the simple charts of case numbers you tend to see each day, but look at them using logarithmic axes, which gives a clearer indication of growth rates, and you see they are climbing.

Not perhaps as quickly as they did in September, but steady, exponential growth all the same.

Cases and hospital admissions have ticked higher in recent weeks after falling for months.

The number of new patients each day has gone up by 30%, from 75 in mid-May to 100 at the beginning of June.

The rise in hospital admissions began two weeks after the increase in cases, mostly caused by the spread of the Delta variant (B.1.617.2), first detected in India.

The increase has been been driven by the North West, which accounted for one in four new admissions in the last two weeks.

The region also has more than half of all Delta cases sequenced in England, according to data from Wellcome Sanger Institute.

The rise of cases and admissions in England is not as fast as in September (darkest shade), the start of the second wave when a similar number of daily cases were recorded.

But in the North West, cases and hospital admissions are increasing faster than the national average, although the growth remains slower than it was at the start of last autumn.

Now it’s easy to look at such charts and conclude that something is going awfully wrong. But let’s not forget, most of the epidemiologists reporting to SAGE expected something like this to happen.

Indeed, it would be odd if the lifting of restrictions didn’t cause a rise in cases, especially among those who aren’t yet vaccinated. And looking at the age profile, most of these cases are among younger people, who are less likely to have been jabbed.

If the second test above is passed – in other words indicating that fewer people are likely to face hospitalisation and death – then it might be that this rise in cases will not put strain on the healthcare system.

However, this judgement is tricky to calibrate. And no-one feels especially comfortable about the prospect of rising hospitalisations.

Even so, given the vaccines seem to be working, it’s perhaps going a little too far to assume that, on the basis of case growth alone, the data is flashing a red signal that implies the timetable should be scrapped.

But now we get to the final of the tests.

4. “Our assessment of the risks is not fundamentally changed by new Variants of Concern”

And here the data is clearly more worrying. Indeed, there’s a good case to say that if the government were taking its rules seriously it might have concluded that this test was failed some time ago.

We know that the Delta variant first detected in India (B.1.617.2) is more transmissible. It appears to be more severe, in that Public Health England says it leads to double the number of hospitalisations in those infected.

We know that the variant has now, very quickly, overtaken the Alpha and Kent variants as the dominant strain of the virus in the country. And the data seems to suggest that it is somewhat more resistant to the vaccines – though this goes primarily for those who have only received a first dose.

Put this together and it is certainly hard to argue that this final test has been comfortably passed. Then again, you could have said this a month ago – the data was pointing in the same direction – yet the government proceeded with step three of the unlocking on 17 May.

This largely comes back to the issue we began with: for all its talk about data, the government is completely opaque about what levels in the data would constitute concern.

Most epidemiologists would say that on the basis of the data, the third and, certainly, the fourth tests now look to be in jeopardy. The government’s own view? We are about to find out.

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